US2351014A - Alarm for synchronous telegraph circuits - Google Patents

Description

J u ne13,1944. h A. F. CONNERY ETAL 2,351,014

ALARM FOR SYNGHRONOUS TELEGRAPH CIRCUITS Filed Dec. 30, 1942 2 Sheets-Sheet J.

V INVENTORSQ HL DER F- CONNER Y ERIC REC- cqa BY ATTORNEYS n 13, 1944. A. F. COQNERY ET AL 2,351,014

ALARM FOR SYNGHRONOUS TELEGRAPH CIRCUITS Filed Dec. 30', 1942 2 Sheets-Sheet 2 R N 0 m QM N (u INVENTORS ELDER F. comvznv Ema R. a. 005

Patented June 13, 1944 UNITED STATES; PATENT O E ALARM FOR SYNCHRONOUS TELEGRAPH v omourrs Q Alder'F. Connery, --Great Neck, N. Y., and Eric R. C. Coe, Chatham, N. .L, assignors to Postal Telegranl cable Company (New York), New York, N. Y., a corporation of New York,

j Application December'30, 1942, Serial No. 470,574 '11 01am; (01.1781-53) The present invention relates 'to' automatic printing telegraphy and particularly to printing telegraph equipment which is synchronously operated. More particularly still, the invention may be utilized in connection with synchronous multiplex telegraph circuits.

Frequently in synchronous telegraphy, and particularly when the interconnecting lines are of considerable length, haphazard signal distortionresulting either from outside interference or'from degradation of the duplex balance results in errors in printing of the telegraph receiver. When the duplex balance is disturbed; distortionof the received signal results, even though there be no outside interference. In many instances in such printing telegraph systems, the printer or similar recording device is left unattended and the invention is of particular use in'connection with such unattended systems although notin any sense limited thereto. In overcoming these difiiculties, we have provided forthe automatic detection of error arising from such haphazard signal distortion. In generalthis is accomplished by sending a special signal from the transmit-1 ting station at predetermined intervalsofi time. This signal is then sought for'by a synchronously operating apparatus at the receiving'end of theline and arrangements are made such that if the signal is abnormally mutilated an alarm will automatically be given. I

It is an object of our invention to provide'a synchronous printing telegraph circuit ywhich will automatically signal the presence'of haphazard signal distortion in undue degree.

It is a further object ofour invention to provide such a circuit which is readily utilized'in connection with the-normal multiplex printing telegraph circuits and-which. is simple and inexpensive of installation. 7

Further objects and features ofthe invention willappear when the following specification is considered in connection with the appendeddrawings, in which s Figure 1 is a schematic diagram of the circuit arrangement as utilized with synchronous. printing telegraph equipment -havingtransmitters electrically connected to send rapid reversals when the transmitters are in. their idle --condi-' tion.- This diagram shows the application of the alarm circuit to a duplexed multiplex circuit. For simplicity, however, equipment for transmission in one direction only is shown. 1 i

Figure 2 is a schematic diagram of a the circuit arrangement .as -,-utilized with --synchronous printing telegraph equipment having trans-,

mitters electrically connected to send slow reversalswhen the-transmitters are intheir idlecondition. This diagram also shows the appli-,; cation of the alarm circuit to a duplexed multiplex' circuit; again equipment for transmission in one direction only is shown. h As has been indicated in the foregoing description the synchronous telegraph circuits are shownas being ,of'the multiplex type.- Although singlechannel synchronous telegraph equipment may be utilized the multiplex system is the mostcommon form of such synchronous telegraph arrangements. v 1

Referring to the drawings, there is shown in- Figure 1 a line l0 which may be either a singleline with ground return,.as illustrated, or a pair. of wiresproviding-ametallic return. Thisli-ne I0 is balanced for duplexoperationin the well known manner bymeans of artificial networks I l. and I2. Likewise in conformance'with usual practice, there are provided the difierential mili ammeters l3 and I4 and the differential polar. relays l5 and IB.-- While difierential duplex cir cuits have been illustrated,it will beunderstoodthat a bridge type duplex circuit can equally wellbe used. The transmitting equipment is connected to the split of the duplex in the usualmanner'and the receiving equipment operatedfrom the contacts of the difierential line relay l5- or IE, likewise in the usual manner. The transmitting equipment shown at the leftin Figure-lcomprises the distributor-l! together with the tape transmitters l9 and 2|, which transmitters are fed from the usual split signalling battery23.- 25 through protective resistance 21 and 29.;

The distributor ll (of which but four rings areillustrated) comprises ten sending segments designated am through 3| 9', a common ringcooperating with the sending segments and-.desig-- nated 3 3, sixth pulse magnet segments designated 35a and 35b and the common ringtherefor designated 31. I Itwill, of course, be understood that this distributor is adapted for two channel transmis sion and that if a greater-number of channels is to be utilized there will be additional sending segmentsand additional sixth pulse magnet segments, there being five additional sending seg-.: ments for each channeland, of course,;a single additional sixth pulse segment for each channel. As stated hereinabove, Figure '1- illustrates the arrangement when the transmitters I are "connected to sendrapid reversalswhen in their-idle position." For this reason alternate contacts of each of the-transmitters l9 and 2I-are'connec'td 0nd and fourth contacts to positive battery. he

lower contacts of both transmitters are connected in each instance to the battery opposite in polarity contact. The armatures of the transmitters. are

connected in the usual manner directly to the.

corresponding sendin segments 3la to-3l:i.'

The above has described thenormal two: chanto that connected to the correspondingzupper sitionshown in Figure 1, a character signal will have just been transmitted over the first or A channel and the brushes will just have connected cornmon ring-fl to segment a thus causing a flow ofcurrent from battery through protec- "itive resistance .41, and conductor 49 to ring 31 nel multiplex transmitting arrangement, it being.

understood that in transmitting, tape is supplied to the two-tape transmitters which are operated: in accordance with the perforations in'. the tape. In applying our invention to this arrangementthe. transmitter (as f or example transmitter P9) of. one channel is: adapted to be held operated, that is to be held to its idle side or with thearmatures against the corresponding upper contacts, for a predetermined portion of the transmission, for example during one distributor: rotation in each ten, whereby'rapid reversals: are transmitted over the line after each group of nine character signals of the samechanne'l.

This is accomplished by providinga cam' 39- which is driven fromthe shaft of distributor ll through a set ofreducing gears which reduce itsspeed to some exact sub-multipleof the speed of the distributor brush shaft, if' the distributor is of the brush type, or-'- in any-event-to one-tenth of thespeed of operation of stated above, we have found a speed of one-tenth that of the distributor to be advantageous; The cam 39 cooperates with a pair of contacts 41, 43 andi is arranged toclose these contacts and hold them closed during' slightly more than one distributor revolution.

' 'At the receiving end of' the circuitthereisprovid'ed theusual equipment comprising a distributor [8 having two segmented rings. Of course, this receiving distributor is provided with'numerousf 'other solid and-segmented rings for correction and like purposes which, however; are-well known a'nd do not enter into the description of this invention. Connectedto eachgroup of se ments 22a through 22c and 22f through 227' is a receiving recorder'which may be either a common t'elegrapl'rprinter; frequently known as a teletypewriter, e1 a*repe rforator or aWtranslator. This-latter pie'ceof equipment is a. device for converting the live unit code of synchronous multiplex telegraphy to the five unitcode utilized-for start-stop operation. Oneexample of-such a translator is that shownin I-Iallden Patent No. 2,196,069 of April 2; 1940; In the diagram of. Figure l the telegraph printers are schematically illustrated by'a showing of their magnet coils. at 2'4 and25. I 1

At the receiving terminal a cam 40, similar to the cam 39-, is provided; the cam being similarly driven at the same sub-multiple of the distributor speed as-is the cam 39. This cam is provided with a pai'r of normally closed contacts 42 and 44 whichare in shunt to the operatin winding of analarm relay-46. Relay 46 is inadditiori providediwithi a locking winding 50-, the--circuit for which. extends frombattery 52' through protec.

the distributor. As

and thence through the brush 35a and conductor 5t to the operating or stepping magnet 53 of transmitter l9. This will cause the transmitter to move all of its armatures to their upper contacts in.the-.normali manner and would normally wh'enzthe distributor. brushleftsegment 35a.cause' the stepping magnettoJde-energize advancing theperforated tape to thenext position and per' mittin the pins of? the. transmitter to cause'the positioning of the armatures upon their'upper or lower-I contacts in accordance'with' the perforations. in the-tapeat: the new position. However, while the" brush is. traveling over segment 35a, cam .39: closest contacts. 41-- and 43 thereby completing'a circuit from battery 45"thr0ugh resistance. andthence over conductor Hand through contacts 41 and43 and' conductor 55 to the operating or stepping magnet 53'. This retains the transmitter'in'itsidle position with the armatures against the upper contacts and-due to the alternate arrangement er these contactswith respect t'othe; split battery 23, 25', as heretofore described, the next signal sent out on the first or A channet will be'oneof rapid reversals. Prior to this time, the'- character signal already set up on transmitterl f'is -sent to the line in the usual manner. Following the transmission of the rapid reversals during the period when transmitter l9 isheld inits idle position'the brushes of the distributor agai'n make contact with segment 35a and 'shortly'thereafter cam 39 in its continuing rotation in a counter-clockwise direction reaches a position such that contacts 4|, 43 are opened. Thuswhen the brush leaves segment 3511' the circuittomagnet 53 is completely broken and this magnet assumes its normal periodic operation untilsuch time-as cam 39 has completed a rotation and returns to substantiall the position illustratedinFigure l;

When the rapid" reversals are received at the receiving polar' differentia'l' relay it, they, of course, cause operation of that relay to connect ground to alternate ones cfthe receiving segments: 20 when inone positionand to the interveni'ng segments when in the other position. The relay- [6 is adapted 'to have its armature move to the righthand contact 30 when a positive signal is received and to move to the contact 32 when a negative signal is received; Thus, if the received signals are inexact synchronis'm with the transmitted signals and there has been no shift-of the crossover between signals resulting from signal distortion, whenever the relay is on its right hand contact 30. it will complete circuits to the second or fourth receiving segments 20 of the distributor l8and since thebrush will, at that time, lie on a first, third or fifth segment 2!! of the distributor," the circuit will be-interrupted at this point. However, when there has been merits 11;- will; be; connected, to the le t; hand on: tact; 3.2; of the; recehdnscrc and. the second and; iourth sesnentswill: be; connec ed to; the ri -htharrd on actim Y 3 Althou h: t e: peration oi: the ircuit: just ab ve e cr bed. is so imilar tothatdescribed; c nne i n wit F g re v as o b imrned a ely pe: parent a br erresumc h reof m yb -'hclnfu iterthe transmi sion of? each nine c ara t signals o er the/A; hannel fr m transmitter 19, z s- 1L; 2; ther bycausins nerationof re ay The perati n f: this re ay reaks the circ. It t the op ratinama net 53' or transmitter, L9 immediately: after-this ;-cir-v cuit; has: been. broken throu h. the sixth pulse masnct se ment 35% 'l'he transm t ris, th ev f re, stopp d to. its; next; positio and remains there during; the succeeding: rotation of, the distrib tor r sh: arm; During this, rota ion, rapid current reversals are, sent; over th line: owing to the alternate connection of segments-.3 la through 3le with positive; and, negative; battery. These rapid, curr nt: rov rsalsare r eived a he r ceiving relay Hi1 at; a; time when the cam. 4,0 has closed contacts 14, I65and,;theref,ore at, a time when relay 12 is operated. If-the signal iswithut undu istortion owin ither to Qutsideinterference or todegradation or the duplex balnce, he rma ure,- of relay l.6;wi lie p n contact 3-2 whenever the. brush f; istributor 1131185 on either they second' orqiourth segments 20 of the; receiving: distributor and upon contact; 30 when, the brush isgOnl either the first, third or firth segments, n, however; there has beenany ndu d st rtion th re will betimes: during which th armature of relay [6: will lie on contact 32 while the, brush is; on, the first; third or'fifth disributor se ments or: on contact 3.0 when the brush: is on the second; or fourth segments; Since the shunt is at; this time; removed fromthe: opcrating,winolirrgv or alarmrelay 46, atcontacts 32, 4,, he e; will result an peration or the relay 46 it th impulse is; or suflicient durations As, de-

scribed in connection with Figure 1;, this relay will lock in, its. operating position and will, in. ad-

dition,;operate the lamp 6llto indicate that the single distortion is approaching the limit; for accurate recording. Also as before, the relay will so operate eventhough the received; distorted si nal' is insufficient. to cause errorsof; operation of the, receiving recorders; which, of; course, may be printers, reperforators, translators, etc; 7 It, will be understood that-the: embodiments of the invention described, are preferred,- embodiments only, and that many modificati'ons-rnaybe employed without departing from the spirit of our invention; For example, the inventionrmay be utilized in connection with a single channel type of synchronous. telegraph system such as; has been mentioned hereinabov-e; Furthermora'the invention may be utilizedwith a regenerative repeater of the rotarytype, although-in this instance the circuit of thetalarm relay 46: would be ea n? of th cir uit nt rc nn cting t receiving and transmitting equipment of the regenerative repeater instead of being in series with the recorder magnets as in the case of,- its use with a synchronous receiving terminal set.

Of course, the alarm signal which has been, def scribed, as a lamp: may be oi anyconvenient type, either-audible or visible. 7 U

Whenever the word recorder is used in the claims, it will beundersto l th t it is. int nded o include not. only the printing, tele raph c iv s, rcp riorators and, anslators. s me i ed in.

therspecificationl bu also he ircui s: nterco e ina he-rcceivina and send ng: equipment of a rotary egener tive epeater s mentioned h r abov Whatisclaimcdiss 1. In alsynchronoustelegrapl system, in com, bination, a transmitting; terminal; comprising a transmitter-and a distributor; a receiving-terminal comprising a. receiving relay, receiving distributor and a. recorder, meansforperiodically interrupting transmission from said transmitter, means fortransmitting a special signal during said period of interruption circuit means controlled jointly-by saidreceiving relay and receiving distributor for normally-rendering inoperative the recorder during substantially undistorted'receptionv of: the special signal, an; alarm device in circuit with the recorder, and means operating synchronously with the transmitter interrupting means forrendering said alarm device operative duringtransmission of thas ccial signal wherebyan alarm i5 iven when said special signal is abnormally distorted during trans;-

mission. 1 p r 2. In a. synchronous telegraphsystem, in com, bination, a transmitting; terminal comprising a transmitter and a transmitting distributor, a, re-. ceiving terminal comprising a receiving relay, a receiving distributor and a. recorder, means driven by the transmitting distributor at an exact sub-multiple of, the speed thereof for holds ing the transmitter its ldle'position during the o t or the distribu or e ebya. i na comprising: rapid reversals of current is transmitted to; the line circuit, means controlled jointly by said receiving relay and receiving dis-. tributcr for normally renderingthe recorder in-, operative during substantiallyundistorted receps tion of the said, rapid reversals of current, an

alarm devicein circuit with said recorder, and means driven bythe receiving'distributor at, an

exact sub-multiple of the speed thereof and-in synchronismwith the; driven means at the transmitting, terminal for rendering said alarm device operative during transmission of said rapid reversals, whereby when rapid reversals are abnormally distorted during transmission said alarm device: is; operated.

3. In a multiplex telegraph system, in combination, a transmittingv terminal comprising a plurality of transmitters and a transmitting distributor, a receiving terminal comprising a receiving relay, a receiving distributor and a plurality of recorders, means forperiodically interruptingrtransmission from cncof said transmitters, means .for' transmitting a special signal during said period of interruption, circuit means controlled jointly by said receiving relay and receiving distributor for normally rendering inop-. erative the recorder associated with the trans-v mitter from which transmission is, interrupted during substantially undistorted reception of the special signal, an alarm device in circuit with the said associated recorder and; means operating syn hr sly w t the. transmitter i t r uptin meansfor rendering said alarm device operative during transmission of the special signal wheres by an alarm is; given when said special signal is abnormally distorted duringtransmission,

4. In amultiplextelegraph system, in combi nation, a transmitting terminal comprising a plurality of transmitters and. a transmitting distributor, a receiving terminal: comprising a receiving relay a receiving distributor and a plur li y of c ders, means r en y the t ans mitting distributor at an exact sub-multiple-of the speed there'offor holding one of the trans mitters in its idle position during a revolutioncf the distributor, whereby a signal comprising rapid reversals of current is transmitted to the line, circuit means controlled jointly by said re-' ceiving relay and receiving distributor for nor mally rendering the recorder associated with the held transmitter inoperative during substantially undistorted reception of the said rapid reversals of current, an alarm device in circuit with the said associated recorder, and means driven by the receiving distributor at an exact sub-multiple of the speed thereof and in synchronism with the driven means atthe transmit. ting terminal for rendering said alarm' device operative during transmission of said rapid reversals, whereby when rapid reversals are abnormally distorted during transmission said alarm device is operated. I

5. In a multiplex telegraph system,'in combination, a transmitting terminal comprising a plurality of transmitters and a transmitting distributor, a receiving terminal comprising a receiving relay, a receiving distributor and a plurality of recorders, relay means for disconnecting one of the transmitters from the corre-- sponding distributor andsupplying said distributor with current from a current source in such manner as to providetransmission of a special signal consisting of rapid current reversals, means driven by the transmitting distributor to periodically operate said relay, said means being driven at a speed. which is an exact submultiple of the distributor speed, a circuit ioining said receiving relay and said receiving distributor, means at said receiving terminal operable in synchronism-with the relay means at the transmitting terminal and driven at a speed which is an exact sub-multiple of the speed of the receiving distributor, said means serving to alter the said circuit connection in such manner that the receiving relay and receiving distributor jointly render the recorder associated with the disconnected transmitter inoperative during substantially undistorted reception of the rapid current reversals, an alarm device in circuit with the said associated recorder rendered operative by the said means, said alarm device being operated upon reception of abnormally distorted rapid current reversals.

6. In a multiplex telegraph system, in combination a transmitting terminal comprising a plurality of transmitters and a transmitting distributor, a receiving terminal comprising a receiving relay, a receiving distributor and a pluralityof recorders, means driven by the transmitting distributor at an exact sub-multiple of the speed thereof for holding one of the transmitters in its idle position during a revolution of the distributor, whereby a signal comprising rapid reversals of current is transmitted to the line, circuit means controlled jointly by said receiving relay and receiving distributor for normally rendering the recorder associated with the held transmitter inoperative during substantially undistorted reception of the said rapid reversals of current, an alarm relay in circuit with the said associated recorder, means driven by the receiving distributor at an exact sub-multiple of the speed thereof and in ynchronism with the driven means at the transmitting terminal for rendering said alarm relay operative during operation of transmission of said rapid reversals, whereby when rapid reversals are abnormally distorted during transmission said alarm relay is operated, and means operated by said alarm relay to give an alarm signal. j v

7. In a multiplex telegraph system, in combination, a transmitting terminal comprising a plurality of transmitters and a'transmitting distributor, a receiving terminal comprising a receiving relay, a receiving distributor and a plurality of recorder means driven by the transmitting distributor at an exact sub-multiple of the speed thereof for holding one of the transmitters in its idle position during a revolution of the distributor, whereby a signal comprising rapid reversals of current is transmitted to the line, circuit means controlled jointly by said receiving relay and receiving distributor for normally rendering the recorder associated with the held transmitter inoperative during substantially undistorted reception of the said rapid reversals of current, an alarm relay in circuit with the said associated recorder, means driven by the receiving distributor at an exact sub-multiple of the speed thereof and in synchronism with the driven means at the transmitting terminal for rendering said alarm relay operative during transmission of said' rapid reversals, whereby when rapid reversals arejabnormally distorted during transmission said' alarm relay is operated, means operated by said alarm relay to give an alarm signal, means to maintain said alarm relay operated after actuation'thereof, and manually controlled means to release said relay.

8. In a multiplex telegraph system, in combination, a transmitting terminal comprising a plurality of transmitters and a transmitting distributor, a receiving terminal comprisinga receiving relay, a receiving distributor and a plurality of recorders, cam means driven by said transmitter at an exact submultiple of the speed thereof, contact means ,operated by said cam means, said contact meansbeing arranged in a circuit in shunt to the normal transmitter magnet operating circuit and serving 'to maintain'the transmitter operating magnet operated during a revolution of the transmitting distributor to cause said transmitter to transmit an idle signal over the line, circuit means controlled jointly by said receiving relay and receiving distributor for normally rendering the recorder associated with the held transmitter inoperative during undistorted reception of the said idle signal, a normally short circuited alarm device in circuit with the said associated recorder, cam means driven by the receiving distributor at an exact sub-multiple of the speed thereof and in synchronism with the driven means at the transmitting terminal, con-.

tact means operated by said cam means and effective to remove the short circuit from said alarm device and render it operable, said alarm device being operated upon reception of distorted idle signals to give an alarm signal.

9. In a multiplex telegraph system, in combination, a transmitting terminal comprising a plurality of transmitters and a transmitting distributor, a receiving terminal comprising a receiving relay, a receiving distributor and a plurality of recorders, cam means driven by said transmitting distributor at an exact sub-multiple of the speed thereof, contact means operated by said cam means, said contact means being arranged in a circuit in shunt to the normal transmitting magnet operating circuit and serving to maintain the transmitter operating magnet operated during a cycle of operation of the transmitting distributor to, causesaia'tran mitter to 'tfafisfiiitan'idlesi nal over" the line, circuit means controlled jointly 169 said receiving relay and recemng "distributor for normally rendering the recorder associated with the 'hltltransmit'ter i'r'ionrative during iindistoft'ea ifcptioncf the said idle "signal, "a "nor many gnbrt iffiited alarm relay in Circuit with the .s'aid associated "recorder; cam means tithe ifiiffii 'dfslifibufifil at all "XaO't 's'ubfl-iritll title "of the sfieed thereof and in synchronism with "the driven "at "the transmitting terminer, contact means operated by said cam means afideffti'vet fm'dv'ethe's'hort circuit from said alarm relay "and render it operable, said "alarm being operative "to give an alarm upon the recebtiofn' of distorted rariid current reversals whereby an alarm is given when substantial distortioh occurs and be'fore'distortibn is effective to bra uceerrbneous'recoraing.

' 10. me rrifiltipliitelgrefph system, in comin nation, a trafisniittifi'g'tfihirfal comprising a pilu rality of 'tr' fiiittfs and a transmitting distributor, a receiving terminal comprising a re"- ceiving'rela'y, a receiving distributor and'a p111- ralitS 'of recorders, relay "means for "disconnect mg on'eof thetrarlsmitt'ers from the'cbrresponw i'n distfiblitti i, iiit 'ri'lipting the Stepping ofsaii'd transmitter aha s plying said distributor with current frbma soiii'ceinsuch manner as'to'cause transmissioh "or 'a'siie'ci'al signal 'co'Inpris-irrg'rapid cufr'e'nt'reversers, means driven by the transmit= ting distributor to jefiodicallvoperate"said -re=- lay, said means being driven ata speed which is anexact sub-multiple of "the distributorspe'ed,

circuits -jbiriin'g' 'said receiving relay and receivmg distributor, a relay-m circuit with the -re comer assbciated "with *the interruptible trans-- mitter, said relay serving 'to' alter the "connections between saidiece'iving relay and'receiving distributor to thereby "render the associated recorder inoperative during undistorted reception 'of the special "signal, an alarm device in circuit with the said ass'o'ciated recorder, '"said alarm-device camper-4 be'iii'grendered operable 'ii'po'n operation of said relay, and cam means "driven 'b'yf-the receiving distributor at an exact "sub-multiple thereof "and in synchronism with driven means at the transmitting terminal to operate "said relay whereby distorted special signals cause operation of said a1arm;device.

11. In a multiplex telegraph system, in combinatioma transmitting terminal comprising a pmrality of trans'mitter's and a transmitting distributor, a receiving terminal comprising a receiving relay, a receiving distributor and a=-1ilur'ality of recorders, relay'me'a'ns -for"d-is'connecting on'e of thetransmitters from the corresponding distributor interrupting the stepping of said transmitter and supplying said distributor with-current from a source injsuch manner as to cau'se transmission of aspecial signal'compr isih'g rapid cii'rrent "reversals, "means driven by the t'ransiriit ting distributor to periodically operate 'saiqii {relay, said means being driven at a speed which is an exact sub=multi1zile of the-distributorspeed, circuits joining said "receiving relay and receiving distributor, a relay in circuit with the recorder associated with the interruptible transmitter;'s'aid relay serving to alt'erthe connections between said receiving relay and receiving distributor to thereby render the associated recorder "inopera tive during undistorted reception of the sfieci'al signal, an alarm "relay in circuit with the ;said associated recorder, said claim relay being rendered operable upohop'eration of said relay, cam means driven by the receiving distributor at an exact sub=multiple of the speed thereof and in "synchronism with the driven-mean's at the transmitting terminal to operat'e 'said relay, same-1am relay beingmore sensitive than'the-recordr,and an alarm device operative by said alarm relay' to give an alarm signal upon the reception or distorted signals-prior to the distortion reaching such magnitude as to be effective to produceerr'oneous recording. v

ALDER'F. GOKNERY. ERIC R. C.'C0E.

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