US2542978A - Traffic actuated control apparatus - Google Patents

Description

Feb. 27, 1951 J. BARKER 2,542,978

TRAFFIC ACTUATED CONTROL APPARATUS Filed Aug. 16, 1949 4 Sheets-Sheet l FIG. I

OCC

ICC

RSC

JNVEN TOR. FIG. 2

JOHN L. BARKER ATTORNEY Feb. 27, 1951 J. L. BARKER TRAFFIC ACTUATED CONTROL APPARATUS .4 Sheets-Sheet 2 Filed Aug. 16, 1949 INVENTOR.

JOHN L. BARKER QM (21M ATTORNEY Patented Feb. 27, 1951 UNITED STATES PATENT OFFICE TRAFFIC ACTUATED CONTROL APPARATUS John L. Barker, Norwalk, Conn., assignor to Eastern Industries, Incorporated, East Norwalk, Conn., a corporation of Delaware Application August 16, 1949, Serial No. 110,559

' 19 Claims. 1

This invention relates to trafiic actuated control apparatus and methods, and more particularly to apparatus for automatic selection among several coordinated trafiic signal timing patterns in response to a sampling of trafiic conditions by traffic actuation.

From one aspect the'invention relates to apparatus for selection among trafilc signal offset systems for one or the other of two traffic directions or for both directions along a roadway in response to trafiic actuation by trafiic in the respective directions, as for example inbound and outbound trafiic directions.

From another aspect the invention relates to apparatus for selection among such offset systems in response to the relative positions of two cycle selectors, one for each traific direction, and each adapted to select one of a scale of cycle positions in response to traffic actuation in its direction over a scale of trafiic volume per unit time period.

From a further aspect the invention relates to apparatus for selection of the higher of two cycle positions selected individually by two traffic actuated cycle selectors from their respective similar scales of cycle positions, one for each of two trainc directions, where different cycle positions are selected by the two cycle selectors, and for selection of the same cycle position where corresponding cycle positions are selected by the two cycle selectors.

Various types of systems are wellknown for coordination of traffic movement through a series of traflic signals along a street or highway. Certain systems of this type provide for the crosstrafijc periods at successive trafiic signals along the highway to come in at progressively later time periods in proceeding along the highway in a given direction for exampleso that the green signal period available for the highway trafiic at the succession of intersections appears to travel along the highway and thus permits fleets of cars to proceed at the designed speed'of the system through the series of traflic signals with a minimum of stopping for accommodation of cross traflic. Such traffic signal control systems are often referred to as progressive systems.

The time lag between any given common reference point in any representative traffic signal cycle in a progressive system and the appearance of the desired corresponding point in the cycle of an individual traific signal in the system is often referred to as the offset for that signal, and it is already well known to provide one set of ofisets for inbound traffic movement in the morning into the center of a city for example, with another set of ofisets for the outbound traffic movement which usually characterizes the heavy traffic flow periods of the late afternoon. In addition a third set of offsets for average or best two-way progressive trafiic movement is often provided for the periods of the day when it is anticipated that the traffic is .not predominantly in one direction.

One difiiculty in such systems however has been that the peak periods of inbound and outbound traffic do not always occur at the same times on corresponding days on week days or on week ends for example and various weather conditions and the occurrence of public events attracting considerable amounts of trafiic will vary the traffic patterns from time to time so that any means.

of setting up in advance a program of the selection of the proper offsets and traffic control cycles' for various times of day and various days of the week is unable to adjust for these irregular l variations.

It is also already known to provide apparatus for selection, by trafiic actuation at a suitable traflic sampling point, between difierent types or lengths of traflic control cycles for the trailic signal system or to adjust the timing of the overall trafiic signal system step by step at short time intervals to accommodate the actual traflicvariationsas they occur. Apparatus of this charactler is sometimes referred to as a traflic cycle selector and my Patent No. 2,288,601 dated July 7,1942 is directed to such apparatus.

In one embodiment of the present invention selection between inbound ofiset, outbound onset and average offset is made in accordance with the relative positions of two. cycle selectors, which may be of the form disclosed in the Patent 2,288,601 referred to for example, as somewhat modified as pointed .out hereinbelow. According to one aspect ofthe invention one cycle selector and an associated traflic actuated detector unit are provided for inbound traflic at an appropriate "sampling point on the highway common to the the two. ofisets.

3 apparatus and offset selector apparatus and associated apparatus serving as a master control system for supervising the operation of the individual trafiic signal controllers at the individual signalized intersections along the highway.

In some cases the preferred location of the cycle selector and offset selector apparatus may be near the middle-of the series of trafiicsignals along the highway and in other cases thepreferred location may be near one end of the series,

in accordance with the best traflic sampling conditions.

In the operation of the selector apparatusfrom its broader aspects the inbound. and outbound traflic streams are respectively ineffect; measured or counted over a time period and duringsuch time period the individual cycle selectors remain on a given trafiic control time cycle for master control of the various individual traffic signal controllers. Near the end of such traffic sampling time .periodthe individual cycle selectors de termine Whether toremain on thesamecycle or to change to. a longer cycle or to ashorter .cycle in. accordance with the trafiic.counted,.for.example. If. the trafiic counted is. substantiall the same as in the precedingsampling time period the. cycle selector remains. on.the. same. cycle .but if the t'raiiicv hasv increased substantially thecycle selector willselect. the next. higher or. longer cycle in the series, or if the. trafiic. countlhas decreased substantially the cycle selector will selectthenext lower or shorter cycle. in. the series. for thenext sampling time period. At .the .end of. each samplingtime .periodthe counting of traffic is reset. and another sampling time. period is started.

-Each.cycle selectorhas. a number ofdifferent cycles to. select from. The Batent 2,288,6D1re- .ierredto illustrates six. cycles or cycle positions A to F for example although it is obvious that more. or. less, could be provided. if. desired,

presentv apparatus-provides a means .of selecting among. the. inbound and'outbound offset systems in.accor.dance.with the positions of the inbound andoutboundcycle selectors. ..For .example ifv theinbound and outboundcycle selectors areboth. on the-same or corresponding. cycle. positions,..indicating substantially the. same traffic flow ineach direction, theoffsetselector.apparatus in accordance with one. aspectof. thepresent invention would select the average. offset. Similarly. in. oneform of..the.. invention lithe inbound and outbound cycle. selectors arenot, more than one cycle position apart the offset. selector will continueto select.the.average...offset. Ontheother hand if. forexample theinbound. and outbound cycle. selectorsare two or more cycle positions apart the offset. selector willselectthe higher .of

Thus. if theinbound .cycle. selector is, two. cyclepositionshigher. .than the out- .bound cycle selectorthe. inbound offset .will be selected by the offset. selector, but. if the outbound-cycle selectoris two: or more cycle positions higher than, theinbound. cycle selector the outbound offsetwill be selectedv by thev ofisetselector.

As described later hereinthe offset selector can be adjustedto. switch to theproperinboundor outbound. olTset when the. cycle, selectors. are .one

cycle position apart if desired, or it. can bev adjusted to switch to. the proper inboundoroutboundoffsetwhen the cycle selectors are threeor .more: cycle-.positionsapart. if desired, .instead of thev two cycle. positionseparation adjustment, just described forexample.

During a large part of the day at most trafllc signal systems along a street or highway there is no predominantly heavy trafiic in either one direction along the highway and the average offset is in general best suited for such relatively balanced trafiic since it is designed to provide best for traiiic movement in both directions through: the series of signals. In sampling traffic for. any relatively short time period it is obvious that there may be momentary or brief periods of increased traffic in one direction which are not truly representative of a continuing condition orevenoi a trend toward such continuing con- .dition. .Under such circumstances it has been :found.desirableto-provide greater stability in the rsystempby requiring the cycle selectors to be more .than one position apart before a change to either inbound or outbound offset and this is the preferred' form of the invention.

It will also be appreciated that the general level of traffic willvary considerably throughout the day andnight. andthat it may be desirable. under circumstances of .moderate traflic but predomi- .nantly inboundtrafiicas .may occur in the early eveninghours. for example tohave the system on an inbound ofiset butata total cycle length of average or moderatelength somewhat between the longest and. the shortestcycles. Itwill beunderstoodi by those skilled in the-art. that the most desirablecycle. length is. related tothespeed and volumeof traific through a series. of traflic sig- .nals, the cycle length being approximately inversely proportional to such speed .for best two- .way. progressive trafiic movement for example, and it will-alsobe understood that as the volume .of. trafiic increases the speed .of traffic tends to decrease and agreater cycle length is needed to .clearthe .trafiic. Thus longer time cycles are better adapted. to care for the greater trafiic volumes and the. lower speeds that ordinarily accompany such. greater trafiic volumes.

Thus at. some. times it willbe desirable to. op-

.erate the signal .system on an inbound oiiset but on a relatively ,longtime cycle and other times .on .aninbound offset at a moderate or shorter time cycle whileat stillother times it .Will bedesirableto operatethe system. on an outboundoffset. for. longer orshorter time cycles.

Thus the presentapparatus according to the present invention is designed to provide. for selection of offsets. up and down the scale of a number of. different cycle lengths so that whichever direction of vtrafiicis predominant will be the..con.trolling'factor and obtain a preferential .ofiset and. at thesametime. obtain an appropri- ..ate cycle length. The apparatus is also designed .to. accommodate average or relatively balanced traffic and to. provide. for theselection of. approvpriatecycle'. length and adjustment of. such cycle length in accordance with'the actual demands of trafiic up. anddownthe. scale. even. if. the traific remainssufliciently balanced to required an aver age. oifset.

Therefore. it is. an object of the invention to provide apparatusand methods for automatic selectionandadjustmentof cycle length and offsettobestaccommodate the volume of traffic in opposite'directions through. a series of traffic control. signals.

It is another object of the invention to select automatically among inbound, outbound and average ofisets in response to sampling of in- ..bound and outbound. trafiic.

It isa. further objectto select among appropri- .ate...tr.afiic.signal timing systems for trafiic pridirections in response to predominant traffic in the corresponding direction, and to bias such selection of offset by maintaining such preferential offset on less predominant traffic than that required to change to such preferential offset.

It is a further object to select among preferen- I tial offsets for each direction and non-preferential offset for both directions along a roadway in accordance with the relative positions of two cycle selectors for the respective directions and each operated by trafiic actuation in its direc-- tion to assume one of a scale of positions corresponding to a scale of low to high time rate of traffic actuations.

It is a further object to provide automatic selection among preferential offsets for one direction or the opposite direction or a non-preferential offset for both directions, in response to predominant trafho in one direction, or in the opposite direction, or substantially balanced trailic in both directions, respectively over a considerable range of cycle lengths for the traflic signaling time cycle at a series of trafl'ic signals.

Other objects of the invention will appear from the accompanying claims and from the following description of the invention with respect to f the drawings in which:

Fig. 1 illustrates in schematic or block diagram form, a traffic control system employing apparatus according to one embodiment of the invention.

Fig. 2 similarly illustrates a series of intersections along a highway together with the individual traffic signals and associated controls and connections with the master control apparatus of Fig. l.

Fig. 3 illustrates a circuit diagram for the off set selector and associated apparatus in accordance with one preferred form of the invention.

Fig. 4 illustrates a circuit diagram of the cycle selector timer employed in'common for two associated cycle selectors.

Fig. 5 illustrates schematically one form of cycle generator which may be employed for variable frequency power in the master control apparatus.

Fig. 6 shows circuit diagrams and offset cam arrangements for two local cycle-offset units of the master control apparatus for controlling the cycle length and offset of two traffic signal controllers.

Fig. '5' illustrates a circuit diagram of one form of traffic signal controller which may be operated on a traflic actuated basis or on a fixed time basis, under control of the master control apparatus.

Fig. 8 illustrates schematically the circuit diagram of a master control unit for controlling the resynchronization circuit for the local control units.

Referring now to Fig. 1 in more detail a section may be a part of a street or highway for example extending through a series of intersections provided with traflic signals.

In one side of the roadway a trafiic actuatable detector unit DDI, indicated schematically as a pair of contacts, is located in the path of traffic in one direction which will be referred to as the inbound traflic direction for convenience of reference. In the other side of the roadway a similar detector unit D is located in the path of traffic in the opposite direction which will be referred to as the outbound traffic direction. These detector units may be of any well known type adapted to close a pair of contacts upon passage of a vehicle thereover, for example,

The apparatus schematically indicated in Fig. 1 represents in general the master control apparatus for a series of traffic signals and associated individual controllers at the several intersections along the highway HY. Several of such intersections are illustrated schematically in Fig. 2 for example, showing the traffic signals ITS, ZTS and 3T8 and associated controllers lTC, 2TC and 3T0 respectively, with local cycle-offset units ILC, ZLC and 3LC.

Returning to Fig. l the master control appara tus includes for example an inbound cycle selector designated I08 and an outbound cycle selector designated OCS, connected to the respective inbound and outbound detectors EDI and DDO.

Instead of each cycle selector incorporating a separate timer for setting up the traffic sam pling period as in my Patent 2,288,601 previously mentioned, for the purpose of the present invention it is preferable to employ a common timer to control the traffic sampling time period for both of the cycle selectors ICE and OCS, and this common timer is illustrated schematically by the block CST between these two cycle selectors and connected to them.

Below the two cycle selectors is a block designated OS illustrating the offset selector apparatus which controls the proper output circuits ICC, OCC' shown at the right for providing the appropriate offset system for the traffic signals in accordance with the relative positions of the.

two cycle selectors, as controlled by the inbound and outbound traffic detectors.

Each of the cycle selectors ICS and 00S is illustrated as having six output connections, corresponding to the six cycle positions A, B, C, D, E, F of the Patent 2,288,601 referred to, and in the present invention these six cycle position connections are illustrated. in Fig. 1 as extending into the block below designated OS for the offset selector unit. In addition to these connections a seventh connection from each of the cycle selectors to the offset selector unit is illustrated which is in addition to those provided in the Patent 2,288,601 referred to, and is for the purpose of indicating to the offset selector when either of the two cycle selectors ICS or 008 is stepping down from a higher to a lower cycle position, as for example from cycle E to cycle D, as will be further explained in more detail below.

As will later be further explained the inbound cycle selector ICS will apply electric power on one of its cycle position output circuits of its A to F cycle scale in accordance with the cycle it is selecting at the moment in response to its measurement of trafirc actuating the traflic detector DDI. Correspondingly the outbound cycle selector OCS will apply power on one of its six cycle position circuits of its A to F cycle scale in accordance with the cycle it is selecting in response to its measurement of traiiic actuating rascega'zs '7 the detectonDDO. Thus these output circuits from the cycle selectors provideinput control circuits: to the: offset; selector'OS: according to which .the offset. selector provides power onits appropriate-output circuitsj.ICC,..OCC to provide. selection-iof the appropriate ofiset forthe traiio-signal system;

Aswill also later be described the apparatus I can beapplied to a trafiic signal system in which the individual signals are. controlled entirely on a: timedbasis. from. the master controller so: that the master controlleralone is controlled by the rtrsrificvactuation, and such'trafiic actuation may come only from the inboundand outbound trailic detectors DDIrandDDO for example.

The. apparatus. may also be employed however in connection with a traffic signal system in which one or more of the individual trafiic signals is controlled jointly by the master controller and. by local trafiic actuation by means of one or .more traific detectors local to the individual in tersections in accordance with one or another of *various well-known types of trafilc actuated traffic signal systems.

Trafficsignal systems of the first type are often referred to as fixed time or pretiined traffic signal systems and those of the second type are often referred to astrafiic actuated signal systems.

Particularly where the apparatus is applied to traffic actuated signal systems the ofiset selector apparatus and its associated output circuits are preferably arranged to provide a means of disconnecting the individual trailic signal controllers from supervision of the master control under certain traflic conditions so that they can respond locally without delay to the traflic actuation of the local traffic detectors. Such operation becomes desirable for example in extremely light traflic as may occur in the late night hours or occasionally at other times during the day. It will be appreciated that if the flow of trafilc becomes so light that there is no particular traflic pattern and there are only occasionai isolated carstraveling along the highway, with frequent occurrence of several successive traffic signal cycles at the various intersections without any interruption of the highway'traffic' in absence of "cross trafiic and thus lack of cross-traffic actuation, it becomes unnecessary to provide'for any progressive flow of traflic through the series of intersections and consequently unnecessary to provide any master control of the timing of the individual trafiic signal controllers. It will also be appreciated'thatin event of failure of the,--'

master control apparatus alone it will be desirable to free the individual traffic signal controllers from 'master control. This is accomplished in one preferred aspect of the invention by releasing the local' traflic signal controllers from master controlby'disconnecting power from both of the circuits ICC and OCC.

The master control time cycle for the different offsets and for the various traffic signal controllers may be providedentirely'fromthe master control point by direct connection individual-lyto the several traffic si nal controllers or maybe provided by running the output circuits ICC-and OCC to the several intersections, and providing individual local cycle and offset units between themaster control and the local signal control but located at each local signal controller to time the proper master control time cycle for the individual local controller, under the supervision of the master controller.

'of the individual traiiic signal controllers can be 8 Various systems"- of; control. are well-known for this purpose. .For example. the individual. local oifset and cycle :units may be operated by synchronous motors so. as to operate eachsuch local unit instep with the master control, and such local unit may be resynchronized once per cycle with the master control. Each such individual control: unit maybe operated on a long or short cycle-in accordance with long or short master control cycles so that the total time cycle of all controlledby the master control, as will be more fully described below.

'Io the right of the offset selector 0S inli ig. 1 there is illustrated schematically a cycle generator unit CG which serves as a master timer'for control of the master time cycle for the several individual traffic signal controller-s at the several intersections. This cycle generator CG is shown connected to six output circuits from the right of the offset selector ()3 corresponding to the scale of six cycle positions A through F forexample. This cycle generator CG may be of the master timer type illustrated in the Patent 2,288,- 601 for example, employing six timing motors for 'six time cycles of various length, in general progressively longer over the scale of A to F for example, and providing individual output-circuits to various individual intersection controllers as disclosed in the Patent 2,288,601 mentioned. However this cycle generator may alternatively provide an output of variable frequency cycle power to operate individual synchronous motors in cycle control timing units associated with or forming a part of the individual trafilc signal controllers at the several intersections as indicated in Fig. 2, and in such case may have the variable frequency power output circuit VCCl, VCC-Z as illustrated in Fig. l.

The output circuits ICC and OCC extending to the right from the offset selector OS represent circuits which are individually actuated to provide the inbound oilset control or outbound ofiset control respectively for the variousindividual controllers at the various intersections for example. As will be described more fully below,

this arrangement permits t is choice of. four di ferent ofisets or cycle control combinations by these two circuits ICC and OCC, b means of which the inbound oliset can be provided by actuation of ICC alone, the outbound offset can be provided by actuation of OCC alone, an average or two-way offset can be provided by actuation of both circuits ICC and OCC together, and still another offset or means of releasing the individual intersection controllers from master control coordination to permit them to operate independently for emergency or extremely light traiiic conditions if desired, may be provided by absence of actuation of either of the circuits ICC If it is desired to provide individual offset circuits at the master control apparatus or in common for the several intersections this can be done by the provision of a master cycle unit as indicated schematically by the block designated MCU at the lower right of Fig. l. which has input circuits above, connecting with the output circuits ICC and CCC of the offset selector, and has output circuits below designated ICC, OOC, AOC, and PRC to indicate schematically the inbound offset, outbound offset, average offset and independent or free operation circuit respectively previously mentioned.

'iThis'master cycle unit MCU is also connected by other input leads shown at the top to the variable frequency power output circuit VCCI and VCCZ of the cycle generator CG, in order to operate the master cycle unit on longer or shorter cycles in accordance with lower or higher frequency cycle power from the cycle generator. The master cycle unit MCU also provides preferably a resynchronizing circuit shown as circuit RSC extending from the right side of the master cycle unit. This resynchronizing circuit preferably extends to all of the individual cycle offset um'ts associated with the individual intersection signal controllers to assure prompt resynchronization in the event of individual controllers or cycle units getting temporarily out of step as a result of power failure or the like.

The circuits OCC, ICC and RS employ a ground return from the individual intersection control units in the form illustrated but may alternatively employ a common wire return if desired.

Referring now to Fig. 2, three intersections are shown as illustrative of a series of intersections along the highway HY. Individual traffic signals for the individual intersections are indicated schematically at ITS, 2T8 and 3T8, and their associated controllers are indicated as ITC, ZTC and 3TC respectively. One or more of the controllers may be of the tr-afiic actuated type as indicated in the case of ITC for example which is connected with detectors lDSl and IDSZ in the side road approaches to the intersection. It will be appreciated that the controllers may alternatively be of the so-called fixed time or nontraffic actuated type, which proceeds through its cycle automatically under control ofthe master cycle control apparatus from receipt of the actuating release impulses to start the individual controller from its rest position at the proper offset depending upon which of the offset circuits is actuated by the offset selector apparatu in the master control apparatus.

In similar manner the trafilc actuated controller will proceed through its cycle of signal indications to accord right of way to the side street and to the highway and come to rest normally with the right of way accorded to the highway until a combination of two events occurs: first, the actuation of one of the side street trafiic detector and second, the receipt of the ermissive or release impulse at the proper offset in accordance with which of the offset circuits is actuated in the master control apparatus One form of local trafiic signal controller under the control of a master control apparatus, is

shown more fully in Fig. '7 and described later in connection with this figure.

Referring now to Fig. 3 which shows the detailed circuit of the offset selector unit, the highway l-IY and the trafiic sampling detectors DDI and DB0 for inbound and outbound traffic are shown schematically again at the top of this figure together with the schematic showing of their associated cycle selectors ICS and OCS and the common traffic sampling period timer CST.

Alternating current power supply wires are shown at the left and right sides of Fig. 3, the A. C. power wire at the right being designated by a plus sign in a circle and the A. C. ground or return wire at the left being designated by a minus sign in a circle. This plus or positive wire preferably provides A. C. at normal supply service voltage with respect to the minus or negative wire at the left for convenience. However a lower voltage A. C. supply with respect to the negative wire is also preferably provided in such case by the wire at the right designated LV in a circle for some connections as described below. Connections for power supply to the cycle selectors ICS and OCS and to the timer CST are provided via wire Hi to negative power at the left and via wire I I to positive power at the right.

The connections from the inbound and outbound cycle selectors ICS and OCS are made from their respective cycle position terminals to the respective input circuits of the ofiset selector below for the several cycle positions. The output terminals of the inbound cycle selector ICS for its several cycle positions are designated AI, BI, CI, DI, EI, and F1 and the corresponding output terminals for the outbound cycle selector OCS are designated A0, B0, C0, D0, E0 and F0. Input circuits are connected from these terminals 'to the operating coils of relays in the oiiset selec-- tor individual to each of these circuits. These input circuits are connected to one side of the coil for each of the relays IA, IB, IC, ID, IE, and IF respectively from the respective output terminals AI through FI of the inbound cycle selector ICS. Input circuits for the relays 0A, OB, 00, OD, OE, and OF in the offset selector OCS are similarly connected from the respective output terminals AO through F0 of the outbound cycle selector OCS. The other side of the coils of all of these relays are connected via wire l2 to the A. C. negative lead at the left side of the figure.

During the trafiic sampling period timed by the common timer CST each of the cycle selectors rests in one of its several cycle positions in accordance with 'a count of the traffic actuations of its associated traflic detector, and near the end of the traffic sampling period determines whether it will step up to the next higher cycle in the series from A to F or remain on the same cycle or step down to the next lower cycle for the next trafiic sampling time period.

Each of the cycle selectors connects A. C. power to the one of its output circuits and terminals corresponding to the cycle position it is then selecting and maintains power on this output terminal until the shift is made to another output terminal near the end of one of the trafiic sampling time periods.

For purpose of illustration in Fig. 2, it is assumed that the inbound cycle selector ICS is in its cycle position C and the outbound cycle selector is in its cycle position E for example, and A. C. plus power will thus be provided over circuits CI and E0 and relays IC and OE in the offset selector will be energized and the remaining relays IA, IB, ID, IE and IF of the inbound group and 0A, OB, OC, OD, and OF ofthe outbound group will be. deenergized as shown in Fig. 3.

Each of these relays is provided with a group of contacts operated by the associated coil and arranged in a vertical line below the coil with a broken line indicating the several contacts associated with their operating coil. When the coil of the relay is energized the several armatures of the contacts are pulled toward the coil away from the contacts on the far side of the armature and toward the contacts on the near side of the armature with respect to the coil, thus closing the latter contacts and opening the contacts on the far side.

In the case of all the relays in this figure the contacts below the armature, that is those on the far side of the armatures, are designated with even number reference numbers and are openedonly when the relay is energizedand'such contacts will be referred to as break contacts'in accordance with widespread practice of those skilled in the 'art. The'contactson the upper side of'thearmature, that is' those nearer the relay "coil, are closed only when the associated relay is energized, andwill be'referred'to as make contacts in accordance with widespread practice in the art. These latter make contacts are designated by odd number reference numbers in the figure. In some'cases, a common armature is employedfor amake contact and a break contact, as shown for contacts zb5 and its for example.

The relay IA is provided with the make contact ial and the break contact 1128. IB is provided with the make contacts 1195, lb! andthebreak contact 1725. The relay IC' is provided with the make contacts 2'05 and i! and the' breakcontact icG. The relay ID is'provided with the make contacts-.idfidl and the break contact z'dfiu The. relay IE is provided with" the make contacts'ie5; is? and the :break contact ie6. The

relay-IF is provided with the make contacts-1Y5, I if! thefbreak contact ifli. The respectiverelays extend: to the right in the figure into the left side of-a -cyclegenerator. indicated schematically 'bythe block'CG. Power is applied from the offset-selectorto the cycle generator over onlyone of these circuits at anyone timepcorre sponding'to the-highest cycle position assumed by -either of the cycle selectors ICS and 008 at that time. For example, with relayIC energized-bycyc1e=selector-'ICSbeing in its 0- cycle positiom-andrelay OE energized by the cycle selector -OCsibeing 111- its cycle E position as previously assumed;- then'power will be supplied from thepositive power-wire at the'right of Fig;

3via-wire'- |3-, break-contact #6; wire 14, break contact ofG, wire l5, breakcontact ze6, wire 17,

make-contact 065;;Wire EGG to the'cycle'gener- H ator CG, thus energizing this wire; While the other wires ACG, BCG, CCG, DCG; and FCG remain deenergized.

7 However if it is assumed for example that both of the cycle selectors ICS and 008 are in their A- cyclepositionthen relays IA and 0A only will be energized in the inbound and out bound-groupsand-power will be applied from the positive power wire-via wire 13, break contact- 276, wire |4;--break contact -0f6; wire l5, break contact ie6,;wire I], breakcontact oefi, wire l8; break contact id6; wire-; break contact odS;

Wire 2|, break-contact 1'05, wire 23, break contact Q65, wire-24, break contact z'bG, wire 26;

break contact obfiwo-wire-ACG to cycle generator 0G,;and the-remainin .WiresBCG, CCG, DSG ECG, and'FCG will be deenergized.

The abovegrouppf circuits-between the relay for the-circuitsACG through FOG to-the cycle generator CG include the following. One cir+ cuit connects contacts ib5 and ob5--inparallel via \vire28-to, WirE'BCG: Another ciruitcon nects contacts 'z'bfiwia'wire 26 to 'thecommon armature of contacts obfi and 0125, and thecon The relay tact ob'E is connected 'to' wi're' ACG. Another Cir cuit connects contact 1'05 -via wire 'to con'-' tact 005 and to \vir'eCCG. Another circuit connectscontact iciivia Wire '23 to the' corninonarmature of contacts 005 and -oc5, -the contact 006"being connected via wire 24 to thecommon armature of contacts iZJS and ibB. Another circuit connects contact id5 via wire 22 to contact 0% and to wire DOG. Another circuit connects contact id-3 via wire 20 to the common armature of contaCtsodB and, od5 andthe contact' odf is in turnconnected via wire 2! 'tothe' com'mon armature of the contacts ic5"and ic5.- Another circuit connects contact ie5 via wire [9 to contact oe5 and to w'ir'eECG. Another circuit connects contact ie6 viawire H to the common armature of contacts oe5"andoe5,

and the contact oefi isconnected via'wirelBto the'common armature of contacts idE and" id6. Another circuit connects contact U5 via wire I5 to contact oj5 and to Wire FOG. Another circuit' connects the contact iffi via wire 14 to the common armatureofcontacts ojiiand offi, and" the'contact ofE is in turn connected via wire 15'- to "the common armature Of contacts z'e5and z'eBfi Another circuit connects plus power via Wirel3 to the common armature of the contactsi/S Another group of circuits-employ the contact groups ial through if! and 0a! through ofl.

These circuits are associated with the selection ofthe inbound'or outbound'ofis'et output circuits ICC andOCC' in accordance with the relative positions of the two cycle selectors ICS-and OCS asindicated by the' closing of one'of the contaots-in the inbourid'and one of the'contacts in the 'outbound group just mentioned' This'se' lection of the offset circuits'is'accomplishedby' the selective operation of oneor the othr'of thetwo relays IRJ-and OR shown tothe-left andright'of two triode tube sections IV and OV shown having acommon tube envelope in thelower part of- Fig. 3. It will be obvious that these tube se'ctions' could be in separate envelopes" but I are 1 shown in the preferred'form with a common envelope;

The re1a'yOR is in the anode circuitoi theinput "winding" TI-Il-Z. of the transformer TH connected via the wires "an'd' 3i to'the inbound and outbound relay contact groups ial through ifTa'nd 0a? through 0f? and by the group of circuitsfrom the armatures of these make contacts to' a rons potentiometer formed by a series of resistors RI, R2, R3; R4, R5shown arrangedverticallyatthe middle of Fig: 3.

Theieft'side TH of the input winding of a the transformer TH is connected Via wire 30 in matures comprising the lower sides of the-make contacts of! andijl are connected in parallel viaw'ire 32 to the upper-end of resistor R1 and also via switch SW3 to the low voltage A: C.

power wire LV at the right sideof the figure. Wire 33 connects the armature of contact oe'l with the common tap between resistors RI and R2.

' This common tap is also connected via wire 34 to the armature of contact iel. The armature of contact d! is connected via wire 35 to the tap between resistor R2 and resistor R3, this tap in turn being connected via wire 36 to the armature idl. The armature of contact 0c! is connected via wire 31 to the common tap between resistors R3 and R4, which tap is also connected via wire 38 to the armature of contact icl. The armature of contact ob'l is connected via wire 39 to the common tap between resistors R4 and RE, which tap is also connected via wire 4!! to the armature of contact ibl. The armature of contact oa'i is connected via wire IiI to the lower end of resistor R5 which is also connected via wires 42 and 44 to the armature of contact ia'l. This lower end of resistor R5 is the lower end of the potentiometer formed by the resistors RI to R5, and is also connected via wires 42 and 43 to the negative power wire at the left of the figure. These resistors RI to R5 are preferably of the same value and together in series provide a potentiometer between the A. C. power line LV at the right and the negative A. C. power line at the left.

In the operation of the oiTset selector, one of the group of contacts cal to of! will be closed in accordance with the cycle position in which the outbound cycle selector OCS is resting at any one time, and one of the group of contacts id? to if'l will be closed in accordance with the cycle position in which the inbound cycle selector ICS is resting at the same time. Byvirtue of the closure of one of the outbound group of these contacts the right side of the input of transformer TH will be connected via wire 3i, via the closed contact to a particular tap on the potentiometer provided by the resistors RI to R5. Corresponsingly the closure of one of the inbound group of these contacts will connect the left side of the input of transformer TH via wire 33 and the closed inbound contact to a particular tap on the potentiometer RI to R5.

For example if the cycle selector I08 is in the top cycle position F and the cycle selector OC-S is in the bottom cycle position A then the contact if"! will be closed and connect the left side of the input of transformer Tl-I tothe upper end or" resistor RI, and the contact cal will be closed to connect the right side of input of transformer TH to the lower end of resistor R5 so that the full low voltage A. C. potential between the positive side LV and the negative power wire will be connected across the transformer TH input with the polarity such that the left side of this input winding will be connected to the A. C. power line LV and the right side of the input winding will be connected to the negative side of the A. C. power line.

However if for example the cycle selector- ICS is in its lowest cycle position A and the cycle selector (JCS is in its top cycle position. F the conditions will be reversed and the left side of the input winding of transformer TH will be connected via closed contact id? to the negative A. (3. power line at the lower end of resistor R5, and the right side of the input winding of the transformer TH will be connected via the closed contact of! to the A. C. power line LV and the upper end of resistor RI, thus connecting the full low voltage A. C. potential across the input winding 14 again but w'ithreverse polarity as compared with the condition previously recited.

If as originally assumed for illustration the cycle selectors ICS and OCS are in positions C and E respectively then contacts ic? and 0e! will be closed as shown in Fig. 3, and the left side of input winding THI-Z will be connected via wire 30, contact 2'01 and wire 38 to the tap between resistors R3 and R4, and the right side of input winding TIII2 will be connected via wire 3!, contact oeI, wire 33, to the tap between resistors RI and R2.

It will be clear from an inspection of the circuit arrangements described for the contact groups id! to if! and call to of! and the potentiometer RI to R5 that if the cycle selectors ICS and'OCS are in the same cycle positions both ends of the input winding of transformer TH will be connected to the same tap on the potentiometer RI-RE and there will be no A. C. power supplied to this input winding, but to the extent that either of the cycle selectors 108 or OCS is above the other in its scale of cycle positions A to F its particular end of the transformer input winding will be connected to a higher A. C. power potential than the other end, and the farther apart the cycle selectors are on their corresponding scales of cycle positions the higher will be the A. C. potential difference applied to the input winding, so that both the polarity and the potential difference applied to this input winding are determined by the relative positions of the two cycle selectors.

The control effect just described on the input winding of transformer TH is employed to control the triode sections IV and 0V through their respective control grids, by connection of the latter to theoutput winding TH35 of the transformer TH, so that neither of the anode circuits of these triode sections are conducting if no potential diiference is applied to the input winding THI-2 or if only a ver low potential is applied to this winding as in the case of the two cycle selectors I08 and 008 bein in substantially corresponding cycle positions. However one or the other of the anode circuits of 7 these triode sections will be made conducting by the efiect of the transformer TH on the respective control grids by sufiicient potential diiferen ence applied to the input winding TI-II-2 and in accordance with the polarity of this potential difierence. For example, if the inbound cycle; selector ICS is substantially higher in the scale.- of cycle positions than the outbound cycle selector OCS, the polarity and potential difference applied to the input winding THI--2 will be such as to operate in conjunction with the polarity and magnitude of the cathode to ground and anode to ground voltages on triode sections IV and 0V so as to make the anode circuit of IV conducting and the anode circuit of 0V nonconducting. On the other hand if cycle selector 00s is in a' substantially higher scale position than cycle selector ICS the potential and polarity applied to the input winding THl-2 will be reversed to make triode OV conducting and triode IV nonconducting.

The grid control of the triode sections IV and 0V is provided by connection with the output winding TH35 of transformer TH, the middle of this output winding at TH i bein connected via wire 46 to the negative A. C. power line. The left end TH3 of this output winding is connected via resistor R8, wire 4! and resistor R6 to the control grid of the triode section IV. The

right end TH5 of this output winding is connected via resistor R9, wire 48,resistor R1 to the control grid of the triode section OV.

The anode circuits of triodes IV and V are connected to the positive side of: the A. C.:line via the respective coils IR and OR and'wire 52. The cathodes of these sections are connected to potentiometer Pl to obtain-fromthe low voltage A. C. circuit L-V a cathode supply potential having the same polarity as the A. C. positive line and of magnitude as determined by potentiometer Pl. When the potential across winding THl--2 is zero or some low value, the. grids are set negative relative to the cathodes to such an extent as to have both triode sectionsIV and 0V in a non-conducting state when-wire'52, is positive with respect to ground. Both triode sections will be non-conducting when wire 52 is negative with respect to ground.

The polarity andmagnitude of the voltage applied to transformer winding THI-2 determines the polarity and magnitude of the grid voltage applied to the two triodes with respect to ground. The Voltages applied to the two gridsare 180 degrees out of phase and therefore only one section can become conducting with any given applied voltage to the primary of transformer 'I.H|2. One section will have a negative potential applied to the grid with respect to ground in additionto the. positive.potential between the cathode and ground during the time that the anode voltage is positive with respect to ground and therefore remains non-conducting. As-v a result of .a-positivergridvoltage of sufiicientmagnitude with respect to ground toovercome: theeffect: of the positive cathode. potentialiwith-respect to ground in theiother section this other section will -become conducting": since-the A. C. potentialv applied to the anode is positive during this time;

The magnitude of thevoltage; across winding THl-2.r.equired' to make oneofthe triodesiconducting is determinedlby the magnitude of thevoltage:on:both'cathodes asset by:potentiometer P-l. One end of this; potentiometer is; connected to.A-. 0'. negative: power via wire. and the other. end is connected via wire 5| to. AC; power wireLV.

Thus the number: of. cycle; positions separation= betweenthe two' cycle selectors vICS and OCS'ZIB- quiredto make. one of" thetriodes conducting; is. adjustable :by meansofpotentiometer PILSO that: the; selection of one or the other. of the twoanode. circuits: of the triode. sections IV: and 0V to select one or theother Ofl the twodirectional' ofiset output circuits: can be: ma'dezto depend on a relatively small. difiference in: traffic: in the 'two directionsor on' a relativelyv largeidifferencerasi desired by the traffic... authorities. Thusthe selection of a preferential offset? for one/directioncan be made to depend on.the offsettselector for that direction being one or two', or more positions aboveithe cycle. selector: for the other: direction.

Also' as will be. more 'fully" described' below this adjustment determines the extent: to which the" intermediate or average offset is maintainedfor somedegreeof separation of: the cycle selectors on their scale of cycle. positions since in one preferred arrangement according to .the inven-- tion: if neither: inbound. nor outbound oil'set is" selected, as byf'both ;.of:'the.aanode circuits of" the triode sectionsrIV andOV being non-conductingthen the intermediateoraverage offsetiis selected. This latter. selection; of the i average offset: may

ii G

16 be made 'for the; cycle selectors I08 and OCS beingat ornear the same cycleposition over the whole scale from A to F, ormay be made only when either cycle selector is higher than cycle position A, as desired. In the latter form of the invention a fourth ofisetor free independent operation for. example. may be provided by both of" the cycle. selectors being in the lowest cycle position A, but the intermediate or average of!- .set provided with the cycle selectors in substantially corresponding cycle positions higher than A.

The-selection of preferential offset for one or theaother' direction or of average oiTset, in arc-- cordance with the degree of. separation of the two cycle selectors-in their scales'of cycle-positions has just been described with switch SW2 in its. closed positionas. shown in Fig. 3.

If switch SW2 is'in its open position the de gree of separation or the two cycle selectors required to change from average to preferential offset can be made greater than the degree required to maintain such preferential offset against change back to average offset. This biasing-action is sometimes desirable to increase the stability of the system of offset selection against too frequent shift of oifset under rapidly varying traffic conditions for example.

This biasing action is obtained by means of the adjustablepotent ometer P2 in cooperation with potentiometer PI and the contacts of the relays IR and OR, as will be morefully described below.

With this biasing control, if two cycle positions separation is'required to select initially the outcontrolled by'adjustment of the relative positions by the two potentiometer PI and P2; With the outbound offset selected for example the potentiometer P! can be adjusted to determine the number of positions separation betweenthe cycle selectors for shifting back to average offset. Then having made that shift the number of positions necessary to shift again to outbound offset for example can be determined by adjusting. of the potentiometer P2 and thereby a greater-separation can thus be provided for initial shift to a preferential offset than is required to maintain such preferential offset.

This biasing action i obtained with the switch SW2 open to make effective-the following circuits shown in the lower part of Fig. 3. The right side of the potentiometer P-i! is connected via wire to the low voltage A. C. power LV. The right side of the potentiometer P2 is also connected via wire 94 to the armature of make contact or? of relay OR, and via wire Sito the armature of the make contact ir'l of relay 1R. Potentiometer P2 as shownserves as a variable resistance.

The variable arm of potentiometer P2 is connected via wire 96 and wire 89 to wire 32, which in turn is connected to the upper end of ie potentiometer ilk-R5. This arm of potentiometer PZis also connected via wire 5" wire 9i to=the make contact OH, and also via wire Thus when either 92 to the make contact irl.

17 of these make contacts is closed by the energization of the associated relay IR or OR, the potentiometer P2 will 'be shunted and the A. C. voltage applied to potentiometer Rl-.-R5 will be reater than with both contacts ir'! and or! open.

Under the condition of either relay IR or OR,

energized; the potentiometer Pl can be used to set the degree of separation of the two cycle selectors that will just maintain the preferential offset. At a smaller degree of separation the offset selector will return to average offset, under which condition relays OR and IR will both be deenergized, thereby opening the shunting of potentiometer P2 by either contact or? 'or ir'l. The total voltage across potentiometer Rl-RS is now less than the condition where potentiometer P2 was shunted, the amount of reduction of voltage depending upon the amount of resistance of potentiometer P2 included in the circuit. With this reduced voltage operating in potentiometer Rl--R5 the degree of separation of the two cycle selectors which will be sufficient to cause either of the relays OR or IR to become energized again and select a preferential offset, will be greater.

The selection of the offsets by actuation of the respective output circuits ICC and OCC is accomplished by operation of the respective relays IR and OR, which are connected in the anode circuits of the respective triodes IV and 0V, the circuits ICC and OCC being controlled by contacts on these relays. The circuit OCC is connected through a break contact ir4 of relay IR. When this break contact ir4 is closed, as when relay IR is deenergized, the circuit OCC is connected via contact irl, and Wire 6| to the break contact ia8 of relay IA, and is also connected via wire 61 and wire 62 to the break contact oa8 of relay OA. When cycle selector ICS a is in any cycle position other than cycle position A the break contact ia8 will be closed and connect positive power via wire 63, wire 64, contact 118 to wire BI, and when cycle selector OCS is in any cycle position other than its cycle position A, then contact oa8 will be closed and positive power will be connected via wire 63, contact 0a8, Wire 62 to wire Bl. Thus if either cycle selector is off of its cycle position A, then wire 6| will have positive power and will supply this positive power over either one or both of the contacts 11 or 014 if either one or both of these contacts is closed.

If cycle selector ICS is in a sufficiently higher cycle position than cycle selector OCS, then relay IR will be energized and relay OR will be deenergized. Thus contact ir4 will be open and contact 0T4 will be closed, and the positive power previously described as applied under this condition to wire Bl will also be applied via wire 65 and the closed contact 0T4 to the output offset circuit ICC. Under this condition the contact 1'1'4 will be open so that the output ofl'set circuit OCC will be disconnected from the positive power on wire 6|.

If on the other hand cycle selector OCS is in a sufiiciently higher cycle position than cycle selector ICS, then relay OR will be energized and relay IR will be deenergized, and in this latter condition the output offset circuit OCC will be energized by the closed contact 11'4 from the positive power on wire 6! as previously described and the output offset circuit ICC will be deenergized because of the open contact 0T4.

If the offset selectors 108 and OCS are not sufficiently far apart in cycle positions however to energize either relay IR'or OR in the anode circuits of triode IV and 0V, then with both of these relays deenergized both contacts z'r4 and 0T4 will be closed and if either cycle selector is off of its lowest cycle A position, one of the contacts M8 and out will be closed as previously described and positive A. C. power will be applied to wire BI and via contacts 2'14 and 0rd to energize both output circuits OCC and ICC.

In the event that it is desired to employ the condition of deenergization of both of the output circuits OCC and ICC as a control for free operation of the individual controllers or for a fourth offset of a type different from the other three offsets for outbound traiiic, inbound traffic and average traffic for example, the positioning of both cycle selectors ICS and OCS in the A cycle position will open both contacts 13:18 and 0a., and thus disconnect wire 6| from the A. C. positive power on wire 63, and with switch SWI in the open position shown in Fig. 3 no A. C. positive power will be supplied to either of contacts ir l or 074 and A. C. power will therefore be disconnected from. the output circuits OCC and ICC even though both of the relays IR and OR are deenergized with both cycle selectors ICS and OCS in position A.

If it is desired however to provide thesame average cycle offset with both cycle selectors in position A as with both cycle selectors in any one of the other cycle positions the switch SW1 can be closed and thus connect positive power 'via switch SW! and wire 66 to contact OM and via wire 65 to contact ir l so that both output circuits OCC and ICC will be energized even with is sufficient so that for any number of positions of separation of the cycle selectors required for a preferential offset selection the change of separation to such number of positions from one less number will produce a change at the grid of one of the triodes to switch that triode from nonconducting to conducting condition.

To limit the grid current drawn by the conducting triode in the event of a large voltage on transformer TH, due to the cycle selectors being several positions apart for example, or due to operation of relay SD, the resistors R6 and R1 are employed in the grid circuits of triodes IV and OV respectively.

Resistor R8 between wire 41 and transformer terminal TH3, and resistor RQ-between wire 48 and 'transformer te'rminal THE, limit the current through transformer TH and the current from the power supply LV when relay SD is operated.

In order to improve the operation of relays IR and OR on the A. C. power positive excursions the capacitors IK and OK are preferably connected across the coils of relays IR and OR respectively.

At the lower left in Fig. 3 a relay SD is shown which is providedjwith make contacts sdt, $115, $611, sdS, and sdl l. The right side of the coil of relaySD is connected via wire 52 to the A. C. positive power wire and the left side of this coil is connected via wire- 53 to output circuits in parallel from the two cycle selectors 1055 and 00S. As will more fully appear by reference to Fig. 4 each of these output circuits connects wire 53 with a make contact on a relay SC in its associated cycle selector. Each cycle selector 19 as disclosed in the aforementioned Patent 2,288,601 incorporates a relay SC which is energized only during the stepping down operation of that cycle selector.

For the purpose of the present invention where a cycle selector is employed of the type having a cyclic switch which has a six step scale of cycle positions and is stepped forward rapidly five positions in order to produce the equivalent of stepping backward one position, as described in the Patent 2,288,601, an additional make contact is preferably provided in each cycle selector on its relay SC. This make contact, which is designated 303, will supply negative A. C. power via wire 53 to the left side of the coil of relay SI) and thus energize relay SD when either one or both of the cycle selectors ICE; and OCS is stepping down.

An alternate arrangement for energizing relay SD may be employed by connecting the wire 53 to the input circuits providing the step down pulse from the common cycle selector sampling period timer CST to the respective cycle selectors ICS and OCS. This alternate arrangement will avoid the provision of additional contacts on the cycle selector relays SC but will cause the energization of relay SD at each actuation of the step down pulse circuit from this common timer CST whether or not either of the cycle selectors is actually stepping down at that time.

With either of these alternate methods of energizing relay SD the purpose of so energizing relay SD is to control circuits to maintain the offset selection in its proper condition during any stepping down operation of the cycle selectors where the cycle selector is of the type that has a six step scale of cycle positions and steps forward rapidly five steps in order to step down one step for example. It will be obvious under such conditions that the cycle selector stepping down will step successively through all of the intervening positions and thus may energize momentarily in sequence the several relays of the IA to IF or OA to OF groups. Since this action would produce artificial transcient conditions of difierent combinations of cycle positions for the two cycle selectors and corresponding conditions of potential and polarity on the transformer TH and on the control grids of triodes IV and 0V as previously described, it is desirable to provide for maintaining the triodes IV and 0V and their respective relays IR and OR, in whatever condition they were at the beginning of this stepping down operation. In other words, during the stepping down operation of either of the cycle selectors, in order to avoid any transient effects the relays IR and OR. are maintained in the same condition as at the beginning of the stepping down operation by the operation of relay SD and its contacts in cooperation with the contacts 21'5- and M5 of relay IR, and the contacts 0T5 and orfi of relay OR as will now be described.

Assume for example that both cycle selectors ICS and OCS have been in cycle position C and C position the relays IR and OR will both be deenergized and will thus have their make contacts 21'5 and 075 open and break contacts W6 and 075 closed respectively. Therefore under these conditions negative A. C. power will be supplied via wire H, make contact sdl 1, break contact ir5, and wire 12 to resistor R8 and to wire 41 and resistor R6 to maintain a sufficiently low or substantially ground grid potential on the triode section IV to maintain its anode circuit nonconducting and maintain relay IR deenergized throughout the stepdown operation during which the relay SD is energized. Also under these conditions negative A. C. power is supplied via wire '18, make contact sd'l, wire 53, break contact orfi, wire M to resistor R9 and to wire 48 and resistor R1, to apply a sufficiently low or substantially ground grid potential to the triode section OV to maintain its anode circuit at a very low conduction or substantially nonconducting level so as to keep the relay OR deenergized during the step down operation.

It will now be assumed for example that the cycle selectors ICS and OCS are in cycle positions E and C respectively at the beginning of the stepdown. operation of either of the cycle selectors and that relay IR is energized and relay OR deenergized. Then as soon as relay SD is energized at the beginning of the stepdown operation low voltage positive A. C. from wire LV for example will be applied via wire 75 and wire 16, via wire 11, make contact sdB, via make contact 1'1'5, wire 12, wire 41 to resistor R5 for the grid of triode section, IV to apply a sufiiciently positive potential on the grid to maintain the triode section IV conducting for energization of its anode circuit despite any opposite potentials supplied to the transformer TI-I by the transient separations of the cycle selectors With respect to their cycle positions during the step down operation of either one. Under the conditions just assumed with cycle selectors ICS and OCS in positions E; and C respectively, relay OR. is maintained deenergized during stepdown operation by the circuit previously described over make contact sdl and break contact 0T6 to maintain substantially ground or low grid potential on triode section IV.

If it is now assumed that the cycle selectors ICS and OCS are in cycle positions C and E respectively for example, with relay IR deenergized and relay OR energized as shown in Fig. 3, immediately before the start of step-down operation of either cycle selector, then relay OR will be maintained energized, during the stepdown operation, by the following circuit. Low voltage A. C. positive power is applied from wire LV via wire '15, wire 76, make contact sd5, wire 18, make contact 0T5, wire '14 and wire d8 through resistor Rl to the grid of triode section OV so as to maintain a sufficiently high positive voltage on this control grid to maintain the triode section OV conducting to hold relay OR energized during the step-down operation. Relay IR is maintained deenergized under the present assumed conditions by the previously described circuit supplying negative A. C. power via wire il, make contact sdll, break contact irfi, wire 72 and wire 4'! through resistor R6 to the control grid of triode section IV.

Thus as descibed above the relays IR and OR are maintained in whatever condition of ener gization of either one energized or both deenergized these relays had immediately prior to the beginning of the step-down operation. This is controlled by the relay SD to maintain this holding condition throughout the step-down operation and then release it so that at the end of the stepdown operation the relays IR and OR. assume whatever condition of energiza-tion and deenergization is needed to correspond with the new steady state positions of the cycle selectors ICS and OCS.

It will be appreciated that if a cycle selector employing a reversible stepping switch is used instead of a cycle selector which steps forward five steps in order to step down one step in a repeated scale of six positions, then the relay SD and its associated circuits via the contacts ir5,

z'rfi, 0T5 and 015 will not be necessary, since in this case the step-down will be directly from one cycle position to the next lower cycle position without intervening transient conditions. 1

In this connection a further protective circuit is provided in connection with step-down operation by the make contact sd3 of relay SD in order to connect positive A. 0. power via wire 8! and contact sd3 to wires BI and 65 so as to maintain A. C. power to contacts ir4 and 0M during stepdown operation of one of the cycle selectors while the other is resting in the cycle A position. This auxiliary supply of A. 0. power to contacts ir4 and 0M under this condition will maintain the power supplied to either or both of the circuits OCC-and ICC in accordance with the opened or closed condition of the respective .contacts ir l and 074 corresponding to the energized or deenergized conditions of their associated relays IR and OR at the beginnin of the step-down oper ation. It will be appreciated that if one of the 1 cycle selectors happens to be resting in its .cycle A position while the other cycle selector happens to be stepping down by stepping ahead five steps from one intermediate cycle position to another intermediate lower cycle position the second cycle selector will momentarily pass through its cycle A position in such step-down operation and this would momentarily disconnect the power supply via the contacts 2'11 and 0M for the circuit ICC to OCC unless this auxiliary power supply via wire 8! and contact sd3 were provided at this time.

It will also be appreciated that this circuit via contact sd3 and wire 8| could also be eliminated if a reversible type of stepping switch is employed in the cycle selectors so the step-down operation could be made directly down one step instead of by stepping up one less step than the total number of steps in a repeated scale of positions, as previously described.

Referring now to Fig. 4 there is shown the circuit and cam diagram for the common sampling period timer CST employed for the two cycle selectors ICS and OCS. These cycle selectors are indicated at the left and right of Fig. 4, and enough of the external connecting wires are indicated schematically in Fig. 4 as in Fig. 1 and Fig. 3 to correlate these units of the master control apparatus as shown in the several figures.

As in the previously mentioned Patent 2,288,601 relating to a single cycle selector employing a single sampling period timer, the present commcn sampling period timer CST employs a continuously operating motor M and the cams S, T, and R- operated by this motor, as shown inside the block designated CST in Fig. 4. These cams open and close periodically the respective contacts SI, TI and RI, in a traffic sampling period time cycle as indicated by the cam contour and the accompanying cam chart showing by the present invention, which employs two cycle selectors, the additional cam contacts S2, T2 and R2 are provided, to be operated by the cams S, T, and B respectively at the same times as contacts Si, Ti and RI, and these added contacts S2, T2 and R2 are connected respectively to the wires extending to the right into the outbound cycle selector OCS, these wires being designated 0-16, 0-, and 0-19 respectively to correspond with the wires 76, i4 and T9 of the cycle selector circuit of Patent 2,288,601 as previously mentioned.

One side of the motor is connected to A. C. positive power via wire I! and the other side of the motor and the cam following members of all the cam contacts are connected to negative A. C. power via wire It, so that negative power is applied to the wires to both cycle selectors when the associated cam contacts are closed, but these circuits are separated from each other when the associated cam contacts are open.

As more fully described in the above mentioned Patent 2,288,601 the sampling period timer may provide a sampling time period of approximately six minutes by one revolution of its cams for example, and during this sampling time period it maintains contacts TI and T2 closed except at the end of the period at which time the contacts are opened briefly to release a counting limit relay in connection with reset of the traffic counting to start a new sampling period. The cam s closes its contacts SI and S2 very briefly at a point somewhat before the end of the sampling time period to pctentialize the cycle selectors to step up to the next higher cycle position if suificient traffic has been counted at that time. The cam R closes its contacts RI and R2 just prior to the end of the sampling time period to potentialize the cycle selectors to step down to the next lower cycle position if insufficient traffic has been counted at this time. The cam R and its contacts RI and R2 also serve to reset the traffic counting for the succeeding sampling time period. Although both cycle selectors are potentialized to step up or down as just described, each cycle selector steps up or down or remains unchanged in accordance with its own trafiic counting independent of the other.

The relay contact SCfi shown in the cycle Se 'lectors in Fig. 4 are connected to wire 53, which extends to one side of the coil of relay SD in Fig. 3 to operate the latter as previously described. The relay contacts SCB are make contacts and are associated with the coils of the relay SC shown in phantom in the two cycle selectors ICS and OCS. The relay SC is energized briefly when its associated cycle selector is stepping down to a lower cycle position.

Referring now to Fig. 5 a circuit arrangement for one form of the cycle generator CG is shown, employing a series A. C. motor designated M and associated A. C. generator driven by the motor M. The speed of the motor M and generator GN is varied by the several circuits ACG, BCG, CCG, DCG; ECG, FCG connected by adjustable taps on the potentiometer P3 shown. in the left side of the block CG. This potentiometer P3 provides resistance in series with the motor circuit, the amount of such resistance being varied in accordance with the particular one of the several cir cuits ACG through FCG energized from A. C. positive power through the operation of the offset selector OS as described in connection with Fig. 3. The offset selector will energize only one of these circuits at a time from A. C. power in accordance with the highest position assumed at that time by either of the cycle selectors ICS or OCS. The A. C. power thus applied via one of these circuits will extend from the associated tap on the potentiometer P3 through the upper part of the potentiometer P3 to the left side of the motor M. the right side of this motor being connected to negative A. C. power. Thus the speed of the motor will be varied and the speed of the generator will be correspondingly varied this wire will supply this A. C. power to a relatively high resistance point on the potentiometer P3 in Fig. 5 to drive the motor relatively slowly in the cycle generator CG so that a relatively low frequency output will be suppleid on the wires VCC-l and VCC2 from the generator GN.

Referring now to Fig. 6 two representative intersections along the highway HY are again shown, together with the master control wires extending along the highway. providing the variable cycle power circuit VCC[ and VCC-2 and the oifset control circuit 000 and ICC, as well as the resynchronizing circuit RSC as previously described. In addition in Fig. 6 however one form of the circuit of the local cycle-offset control unit is shown. The circuit is shown for each of two local control units [LC and ZLC, illustrating that the circuits may be the same although the positions of the cam or other suitable devices for providing the individual offsets for the individual traflic controllers may be different at different intersections.

Thus the circuit and cam arrangement for the local cycle offset unit !LC is shown at the left of Fig. 6 and the circuit and cam arrangement for the unit 2L0 is shown at the right. The two cam arrangements illustrate twodifferent sets of ofisets for the two traffic controllers [TC and ZTC for the respective signals ITS and ZTS, as will be noted from the different positions illustrated for the respective sets of cams.

Referring now to the circuit for the local offset unit [LC at the left of Fig. 6, three relays are shown EBR, [AR and IRS, the designation of the relay being applied to the coil and the associated contact being indicated by a broken line extending from the coils to the armatures of the contacts as previously described and illustrated in connection with Fig. 3. To the right of the relays a motor driven group-of cams CR, ICA, [C1, and [C0 are shown, and to. the left of these cams a.

-,-group of cam contacts, operated by the respective cams, are shown and designated ISR, ISL [S2 and [$3.

The several cams are rotated by the synchronous motor [M which is energized preferably via an amplifier [AM from the variable cycle leads VCC-[ and VCC-2 to which it is connected as shown. The right side of the output of the am plifier is continuously connected to the coil of the motor [M and the left side of the amplifier output is connected to ground, and is completed to the motor coil via a break contact [m4 of relay IRS, and a cam contact [SR connected in parallel by wire [24, either of which contacts may complete the circuit over a wire i23 to the motor coil. The motor [M is operated at a slow or fast rate a desired in accordance with the relatively low or relatively high frequency power on the variable frequency power circuit VCC-[ and VCC-2, so long as either cam contact [SR or relay contact lrs i is closed.

Resynchronization is provided once per cycle by the cooperative action of these contacts with relay IRS being under control of the master control unit MCU of Fig. 1 and Fig. 8. The latter unit contains a resynchronization control cam MCR. For best continuity of service cam MCR is shaped to open its contact MSR for a slightly longer period than the local unit cams [CR and ZCR for example. The internal apparatus and wiring of the master control unit MCU is shown in Fig. 8.

The master control resynchronization cam MCR will close its associated contacts MSR throughout all but a small part of its cycle and open these contacts briefly for this small part of its cycle. The notched portion of cam [CR shown at the left of the cam is illustrative of the part of the cycle during which the contacts [SR are opened. Thus it wil be understood that the cams [CR and 2GB of Fig. 6 will be rotating in synchronism with the similar cam MCR in Fig. 8. When cam MCR opens its contacts positive power will be disconnected from the resynchronizing wire RSC common to the several intersections along the highway HY. This deenergization of wire RSC will deenergize relays IRS and ZRS as shown in Fig. 6, thus closing the break contacts [rs4 and 21's4 to complete the left side of the coil circuits from the motors [M and 2M respectively to their respective amplifiers.

Thus if by reason of a momentary power failure or some other factor the motor [M and its associated cam group were to fall behind the master control unit MCU, the cam [CR would open its contacts [SR at the end of its cycle in the approximate positon shown in Fig. 6, and if it is sufliciently behind the master control cam MCR the. latter will. already have reenergized wire RSC and relay [RS and thus already have opened the contacts [1'84 so that the motor [M will be disconnected from power and stop until the master control unit completes its cycle to reopen contacts MSR and deenergize wire RSC. At such time, with the deenergization of the wire RSC and relay [-RS, power will be reapplied to the motor [M via the break contacts lrs4, and the cam [CR and the associated cams below will be restarted in synchronism with the master control unit again.

On the other hand if the local control unit [LC should by any circumstance be ahead of the master control unit MCU then as soon a the cam [CR reaches the approximate position shown in Fig. 6 in its cycle it will stop the motor [M by 25" opening the contacts ISR,--since itis'assumed that the corresponding cam in the -master control unit has not yet openedv its associated cam contacts at this time to deenergize wire- RSC and thus the contact Irs4 is open. The motor IM will thus remain at rest until the master control cam MCI-t reaches a position corresponding with ICR, at which time the cam MCR will open its contacts, deenergize RSC and relay IRS to reconnect power to the motor IM via contacts Irsd as previously described, and the local unit ILC will then proceed through its cycle in synchronism with its master control unit MCU.

The relays IBR and 'IAR in the local cycle offset unit ILC, are provided with contacts as follows. Relay IBR has the make contact Ibr3 and the break contact Ibr4 operated by a common armature. The relay IAR has the make contact Iar3 and the break contact Iar l operated by a common armature, and the make contact Iar5 and the break contact Ia'rB operated by a common armature.

The offset control circuits for the offset cam contacts ISI, ISZ and IS3 are connected to be placed into operation by the contacts of relays IBR and IAR in accordance with the actuation of the circuits ICC and OCC by which these relays are controlled in accordance with the selection of offset by the offset selector 05 as described in connection with Fig. 3.

Thus with the circuit ICC deenergized and the circuit OCC energized as illustrated in Fig. 3 for the assumed condition of the inbound cycle selector in its cycle position C and the outbound cycle selector in its cycle position the relay IBR will be deenergized and the relay IAR will be energized as illustrated in Fig. 6. Under this condition ground or A. C. negative power will be applied via break contact Ibr4', wire I2 I, make contact Ian-5, wire 00C to cam contact I83. The remaining circuits AOC and IOC to the cam contacts ISI and ISZ will be disconnected from negative power because of open contacts Ibr3 and Ian-4 respectively. Also the wire FRC will be disconnected from the A. C. negative power because of the open contact IarB. Thus the only one of these four circuits receiving negative power via the contacts'of relays IBR and'IAR; is the circuit OCC, connected with the cam contacts IS3. These contacts IS3 are opened and closed cyclically in accordance with the contour of cam ICO which is determined as desired for the outbound offset for the associated traffic controller ITC and its traffic signal ITS. With the circuit conditions with the outbound circuit OCC only energized as just described the cam contacts IS3 will cyclically app'y negative power for brief periods via wire IPC to the traffic controller ITC, under control of the outbound ofiset cam ICOO. If it is assumed however that the offset selector OS is selecting an inbound offset in response to heavier inbound traffic, then the circuit ICC will be energized and the circuit OCC deenergized; Under these latter conditions the relay IBR will be energized and the relay IAR will be deenergized. Then the relay contact 'Ibr4 will be open, thus disconnecting A. C; negative or grounded power from the wire 000 as Well as the wire FRC, and relay contact lbr3 will be closed, thus connecting this power via the wire I22 and break contact Iar-I to wire IOC and cam contacts ISZ which are under the control of the inbound cam ICI. With make contact Iar3 open under these conditions thewire ADC is also disconnected from the negative power and thus theinbound ofiset set cam 26' cam'contacts IS2 are the only ones effective to connect negative power to the traffic controller ITC via the wire IPC, thus making only theinbound offset effective for this controller.

If it is now assumed however that the average or intermediate offset is being selected by the offset selector due to substantially balanced traffic actuations in opposite directions along the highway HY, then both wires OCC and ICC will be energized and both relays IBR and IAR will be energized. Under these assumed conditions negative power will be supplied via make contact Ibr3, wire I22 and make contact Iar3 to wire A00 and the cam contact ISI operated by the average off- ICA. Since break contacts Ibr4 and lard are open under the latter assumed conditions the other circuits IOC, OCC and PEG can not supply the negative power to wire IPC; and the wire AOC is the only one which can supply negative power via cam contacts ISI and wire IPC to trafIic controller ITC so that the latter is controlled on the average offset by the cam ICA.

If it is assumed however that both wires OCC and ICC are deenergized, as for example by selection of free offset operation in accordance with both cycle selectors 10s and OCS being in their cycle A positions, then both relays IBR and IAR will be deenergized, and the wire FRC will be supplied with negative power via break contact Ibr l, wire I2I and break contact Iarfi. Wire FRC thus supplies negative power directly and continuously via wire IPC to the traffic controller ITC under these conditions and the cam contacts ISI, ISZ, I53 are obviously ineffective to control wire IPC.

Thus in accordance with the selection of the oifset control circuits OCC and ICC by the offset selector in response to a determination of the time rates of trafiic actuation in the respective directions along highway HY, each local cycle offset unit will provide appropriate offset control to its local trafiic controller by means of an offset control cam in the local cycle offset unit which is maintained in synchronism with the master control unit; and in the event of extremely light traffic conditions or any interruption of power on both circuits OCC and ICC, each local cycle offset unit will provide free or independent operation of the local traffic controller. It will be appreciated that the circuit for the local cycle offset units 2L0, 3LC and the like are the same as described for the unit ILC, except for the relay and contact designations which are coded for the respective units as indicated in Fig. 6 for 2L0.

Referring now to Fig. '7 the circuit of one form of traffic controller ITC is illustrated schematically. This circuit is primarily that of a simple form of a traffic actuated controller but is provided with a switch SWF which can be closed to convert the controller from trafiic actuated to fixed time operation if desired, and thus serves to illustrate both forms of operation under control of the several offset systems via the wire IPC shown entering the lower part of the rectangle ITC.

The controller ITC as illustrated in Fig. 7 is provided with a synchronous motor TM and a series of cams rotated by this motor. Three cams TCS, TCR and TCM are shown in Fig. 7. The

cam T08 is illustrative of one of a group of cams ordinarily provided in a traffic controller unit for operating the several signal circuits of the traffic signal ITS providing preferably the usual green, yellow and red signals for the respective intersecting streets. Since the cam controlled operation of such signal circuits is already well-known as disclosed in the Patent 2,279,896 of H. A. Wilcox for example, only one of such cams is illustrated in Fig. 8 as TCS to correlate the positions of the other cams TCR and TCM with respect to the high way green signal period, the cam TCS controlling the cam contacts TS-I shown at the right of the cam to control the highway green signal of the trafiic Signal ITS via wire 'III]. The cam TCS is shown near the end of the highway green signal period with positive A. C. power connected via the cam contacts TS-I and the wire I I to the traflic signal ITS.

The cams TCM and TCR control the operation of the motor TM driving the several cams under control of relay IRD and the wire IPC on the local cycle offset unit ILC of the master control apparatus. The motor TM is preferably of the synchronous type and has the left side of its coil connected to A. C. positive power, and the right side of its coil connected via wire II I and wire I I 2 to the junction H3 connected between the relay contact H113 and the cam contact TS-3. The latter cam contact is controlled by the cam TCM which, as indicated by its contour, opens the cam contact TS-3 near the end of the highway green period provided by cam TCS. With the cam contacts TS3 open as shown the motor is able to receive negative power for operation only via the relay contact Ird3 or the switch SWF from the wire IPC from the local cycle offset unit ILC. If traffic actuated operation of the controller I TC is assumed, the switch SWF will be open as shown in Fig. 7, and thus the motor TM will receive negative power for its operation in the position shown only via the relay contact Ird3. This relay contact is controlled by the relay IRD which in turn is controlled by the traflic actuated detector switches lDSi and IDSZ which are shown connected in parallel. These are the detector switches which are located in the side street approaches to the intersection controlled by the signal ITS and the controller ITC.

The left side of the coil IRD is connected to positive power and the right side of this coil is connected via wire TM, and either of the detector switches IDSI or IDSZ to negative power if one of the latter switches is closed by trafiic actuation. Momentary closure of one of the latter switches by traflic actuation by a vehicle approaching on the side road for example will momentarily energize the relay IRD by applying negative power to the right side of its coil via wire H4. In the position of the cams shown, after such initial actuation, the relay IRD will be maintained energized via wire H5 and its make contact I rd5 and the cam contact TS-2 to negative power, the latter cam contact being controlled by the cam TCR and being closed at this time.

Energization of relay IRD as described will close its contact Ird3, and with the cam positions as shown near the end of the highway green period, will connect the right side of the motor TM via wire III, wire 'II2, junction 'II3, relay make contact IrdB to wire IPC. The wire IPC will have negative (grounded) A. C. power applied to it via one of the cam contacts ISI, ISZ, or IS3 of the local cycle offset unit ILC, depending upon which offset is operative as selected by the offset selector as previously described in connection with Fig. 3, unless free operation is being selected by the offset selector, in which latter case the wire FRO in the local cycle offset unit ILC will supply negative power continuously over circuit IPC.

Assuming for example that the outbound offset is being selected with the cycle selectors ICS and OCS in their positions C and E respectively as previously described, them the cam ICO in Fig. 6 will periodically close its contact [S3 for a brief period once per cycle and connect the A. C. negative or grounded power for this brief period via wire IPC to the controller ITC. This brief period is sometimes referred to as the permissive period for the controller ITC, and the application of power for the permissive period is referred to as the permissive pulse, this pulse being provided by whichever of the offset circuits AOC, IOC, 00C or FRC is operated in connection with the selection of ofisets by the offset selector.

Thus when the permissive pulse of negative power is provided on the wire I PC and the relay IRD is energized in the traffic controller ITC by trafiic actuation for example, this negative power supplied by the permissive pulse on wire IPC is connected via contact Ird3, and wires 1 I2 and III, to the motor TM to start the motor. The operation of the motor rotates the cams TCM, TCR, and TCS in a clockwise direction as shown to start these cams through one trafiic control cycle for the signal ITS. The cam TCS deenergized the wire "H0 to disconnect the highway green signal and the cams of the controller ITC continue through their cycle providing a side street green period and then a highway green period before returning to rest in the position shown in Fig. 7 near the end of the highway green period. During this cycle of operation the cam TCR opens its contacts TS-2 during the side street green period and deenergizes the relay IRD, thus reopening the contacts Ird3 and Ird5 and preparing the relay for subsequent trafiic actuation.

The motor TM is operated initially from its rest position shown in Fig. 7 via the contact M113 and wire IPC as previously described, but as soon as cam TCM has rotated out of the rest position shown it will close its contacts TS-3 and apply negative power via wire H2 and III to maintain the motor TM operating throughout the remainder of the traflic signal cycle until the cam TCM reaches again its rest position shown, at which time the motor will be stopped by the reopening of the cam contact TS3 unless there has been a subsequent traffic actuation of reenergize relay IRD and the permissive negative power is again available on wire IPC.

The operation of the controller ITC as a fixed time or non-trailic actuated controller is illustrated for example if the switch SWF is closed in Fig. '7, whichwill connect the permissive pulse wire I PC directly to the motor TM via the wire II I. It will be obvious that the permissive pulse via wire IPC must be of sufiicient length to enable the motor TM to drive the cam TCM out of the rest position and reclose its contacts TS3.

It will be appreciated that the motor TM may be operated if desired from the variable frequency power Wires VCC-I and VCC-Z via an amplifier similar .to the amplifier IAM of Fig. 6 for example to automatically vary the time cycle of the cams TCS, TCR and TCM and the corresponding time cycle of the trafiic signal ITS in accordance with the shorter and longer time cycles provided from the cycle generator CG in the master control apparatus of Fig. 1 and Fig. 3. In this form of operation the left side of the motor TM is connected to the right side of the amplifier instead of directly to positive A. C. power.

It will be appreciated that the trafiic controller cams may be operated step-by-step by a ratchet their associated cam contacts if desired, in the local cycle offset unit ILC.

Although a cycle generator of a type employing a variable speed motor-generator is illustrated in Fig. 5 it will be appreciated by those skilled in the art that an electronic variable frequency generator may be used if desired, such as the familiar audio frequency generator employed in electrical laboratories, in the cycle generator in place of the motor-generator unit shown.

Although a number of alternate forms of arrangements of apparatus according to the invention have been pointed out above it will be obvious to those skilled in the art that other modifications of the apparatus or in the arrangement or character of its parts may be made without departing from the spirit of the invention.

I claim:

1. In a trafiic control system, preferential offset control circuits individual to each of two direc-.

tions along a roadway, means for counting trafiic per unit time individually in each of such directions, and means for actuating the control circuit for either direction in response to measurement of a substantially higher rate of traffic per unit time for that direction as compared with the other direction.

2. In a traffic control system, preferential offset control circuit means individual to eachof two directions along a roadway, non-preferential offset control circuit means for traffic in both of such directions, means for counting traffic per unit time individually in each of such directions, means for actuating the preferential offset circuit means for either one direction alone in response to measurement of a substantially higher rate of traffic per unit time for such one direction, and'nieans for actuating the non-preferential offset circuit means in response to measurement of substantially the same rate of trafiic per unit time in both directions.

3. A structure as in claim 2, and including means-controlled by actuation of one alone of said preferential offset circuit means to bias said circuit actuating means to maintain such one circuit means actuated for a smaller differential traffic ratethan that for actuating it initially.

4. In a traffic controlsystem having two preferential offset systems, one for each of two opposite directions along a roadway, the combination of trafiic actuated means individual to each of such directions, means for measuring the time rate of trafiic actuations of the respective traffic actuated means, and means controlled by said measuring means for selecting the preferential offset system for whichever direction has a predominating rate of traffic actuations, and time controlled means for periodically resetting said measuring means.

5. In a traffic control system having a cycle selector and associated traffic actuated means for each of two traffic directions along a roadway, each such cycle selector having a multiplicity of output circuits representing a scale of cycle positions any one of which may be assumed'by the cycle selector corresponding to a time rate of trafi'ic actuations of its associated trafi'ic actuated means, an offset selector apparatus having input circuits for connection to the output circuits for the respective cycle selectors to be actuated thereby in accordance with the positions assumed by said cycle selectors, said offset selector apparatus also including output circuits for preferential offset systems for the respective traffic directions, and means forming a part of said offset selector apparatus to actuate the one output circuit for whichever direction has a materially higher scale input circuit actuated.

6. A structure as in claim 5, and including means for predetermining at more than one the number of positions of separation of said cycle selectors for such selection of one preferential offset.

7. A structure as in claim 5 and including means for providing an adjustable degree of separation of the positions assumed by the two cycle selectors for selection of either one preferential offset.

8. A structure as in claim 5, and including a multiplicity of output circuits from said offset selector apparatus corresponding to the scale of cycle positions of the cycle selectors and meansfor actuating only one of said last named output circuits at a time in accordance with the highest cycle position assumed at such time by either of the cycle selectors.

9. A structure as in claim 5, and including a multiplicity of output circuits for providing a selection of cycle lengths over a scale corresponding to the cycle positions of such cycle selectors, and means forming a part of said offset selector apparatus to actuate only one of said last named output circuits at a time corresponding to the highest cycle position assumed at such time by either of the cycle selectors.

10. A structure as in claim 5, and including output circuit means for an offset system for traffic in both directions and means forming a part of said offset selector apparatus to actuate the last named output circuit means in response to actuation of input circuits for substantially the same cycle positions for the two cycle selectors except for both of said cycle selectors being in their lowest position on their scale of positions, and additional output circuit means for a system of offset control to permit individual trafiic signal controllers to run through their cycles independently, and means for actuating said additional output circuit in response to actuation of input circuits for the lowest cycle position for both cycle selectors.

11. A structure as in claim 5, and including output circuit means for an offset system for traffic in both directions and means forming a part of said offset selector apparatus to actuate the last named output circuit means in response to actuation of input circuits for substantially the same cycle positions for the two cycle selectors.

l2. Selector apparatus for traffic control systerns, including input circuit means actuatable to represent a scale of low to high traffic flow rates for one traffic direction, second input circuit means actuatable to represent a substantially similar scale of low to high trafiic flow rates for -a second traffic direction, output circuit means for a control system favoring trai'lic in the first direction, second output circuit means for a control system favoring trafiic in the second direc tion, and third output circuit means for a con-,

trol system providing for substantiallybalanced traffic movement in both directions, and means 31 interconnecting said 'input circuit 'means with said output circuit means to actuate -said first output circuitmeans alone in response to actuat-ion-of l said 'first 2 input circuit means at a substantially-higher trafficflow'rate'thansaid secon'd input circuit' means and to actuate-"the secondoutputcircuit means alone-in response "to actuation of-sa-id second input-means at a substant-iallyhighertraific-flow rate-than said first input circuit means, and said interconnecting means 'also in'cluding meansto' actuate said third output circuit means in response to actuation of the first and second input circuitmeans at substantially thesame'tr-affic flow rate.

13. Selectorapparatuses-in claim 12 and in which-said interconnecting circuit means includes an impedance element the impedance of which is controlle'd by said input circuit means in-accordance- -withthe relative positions 'of saidinput circuit means'ont'heir respective scales of -traffic flow rates, and an impedance responsive'device controlled by said impedance element tO-SWitOh among 'said several output circuit means as aforesaid.

14.:Selector apparatus as inclaim l2 andin which said interconnecting circuit means includes -;a ipotentiometerelementcorresponding to the scalesofitraffic rate offlow of said input circuit means, "a .potential responsive element differentially responsive to predetermined potential'of opposite :.po1arity, and connecting means controlled -t byi'the respective input circuit 'means to connect'potential from various vpoints on said potentiometer tozsaid potential-responsive ele- 111E111; ntoapply a.'potentialdiiference to the latter .oftdegree characteristiciof theidegree of sepa ration of .the respective input circuit 1 means as actuated .-.alongtheirrrespective scales of :trailic rate of flow and of polarity characteristic of the higher TOf the two'input circuitrm'eans on the scale iofitraflic lfiow rate.

15.;In an offset selector apparatus, :a multiplicity of input :circuits including corresponding :groups for each rof two trafiic directions and representing substantially corresponding .scales :of-trafficfiow values, ,output circuit means:pro viding l. for traffic signal system oiisets' individual to'the two directionsiand an intermediate offset for lei-directional traffic, sand selector means forming a partof said apparatus for receiving actuations from the respective input circuit groupsto actuate the output circuit for azdirectional offset in response tozactuatio-n of a materially higher scale input circuit for the corresponding direction group than for-theother direction group, and means forminga part of said selector -means for actuating the 'intermediate output circuit means .in response .to actuation of input circuits of substantially-the same scale position for the two directions.

"16. In an offset selector apparatus as inclaim 15, said selectormeans including a series of impedance elements connected to provide ar-multi- -tap,.potentiometer, a potential responsive element differentially responsive to potential ofrdifierent .polarity, connections between the respective input-circuits and said taps, and-means actuated by said.potential.-responsive element to actuate said output circuits in response to'the actuation of the :respective input circuits.

17..:In; an: offset, selector apparatus as. iniclaim 15;;said selector means includlng'a seriesof imipedanceelements connected to .provide a -mu1t-i- :tap potentiometer between "A. .0 power and ground terminals a-transformerwhaving input and output windings, switch means individual to and controlled-by the respective input circuits for the respective directions and including one switch for-each 'direction'for each position on the scale cftraificflow values and operable in response to actuation of its controlling input circuit to connect the correspondingtapon the potentiometer to the input winding of said transformer, the switches ior-onetraific direction connecting to one end of said input winding and the switches for the second traffic direction connecting to'the opposite end of said inputwinding, a connection from a center-tap'on said output winding to ground-two' triodo tube-sections, connections between one-endof=saidoutput winding and the grindof one-said section and'between-the other end-of said output-winding and the gridof said other'section, connections'between the cathodes of both sections and-an A. C. potential intermediate said power and ground terminals, and anode circuits'in'dividual to the tWo-triode sections and controlledby the respective grids to actuate one-anode circuit only in response to connection toasubstantially higher scale potentiometer tap for the'first direction than for the second direction and to'actuate'the otheranode circuit only in response to connection to asubstantially' higher scale potentiometer tap for the second direction than for the first direction, whereby neither of said anode circuits will be actuated in response to connection to substantially the same scale tap on the potentiometer for-two directions, and means for actuating the respective output circuits for the respective directions in responseto actuation of the respective anode circuits and for actuating the intermediate output -circuit in.response"to non-actuation of both .isaidnanode. circuits.

ZISUInH-a selector apparatus responsive to the relative positions'ofxtwo cycle selectors each having .a scaleof cycle positions which it assumes one'at a'time for a;trafiic sampling'time period in :accor'dancewith trafiicsampled in a different one .ofztwotrafficzrdirectionsin a preceding such 'timezperiod, .aljfirst group of relay and input circuits :for "actuation of said relays individually insresponsetoithe position assumed by afirst of saidracycleselectors,asecond group of relays and inputccircuits 'foractuaticnof said latter relays individually in responseitot the positionassumed tby'the :second of said cycle selectors, contact means'form-ingarpartzof the, respective relays to :be:operatedbyractuation thereof, a series of impedance; elements connected between A. 0., power and: return terminals to provide a potentiometer witha multiplicityiof taps,-a transformer having input and output windings, a pluralit of circuits connecting-oneend of said input winding to therespectivetapson said'potentiometer, each circuit including one of said contactmeans closed by.-actuation .oiits associated relay of the'first group-another pluralityof circuits connecting the otherendiof saidzinput winding with said respective taps, andeach including'one of'said contact means closed byiactuation of its associated relayofthe second group, aconnection'frcm the oenterof 'thecutput winding'to said A. C. return terminal, two triode tube sections, a connection fromea potential intermediate saidvA. C. "powereandrreturn terminalsto the cathodes of .both said :zsections, anode circuits individual :to the :two' tube sections,v connections between the respective ends:of :the output winding and the control rgridstof .the :respezitive-sections for actuating onei'anode circuit;in'response:to;a.pre-

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