US2833920A - Electronic matrix commutator - Google Patents

Description

May 6, 1958 T. L. BULEY 2,833,9120

ELECTRONIC MATRIX COMMUTATOR JNVENTOR. THEoDoRE I .BULEY ATTORNEY T. L. BULEY ELECTRONIC MATRIX COMMUTATOR 1MEG.

May 6, 1958 Filed March 30, 1953 INVENTOR.A

ATTORNEY TH EQDORE L. BULEY FIG. 4

United States Patent() M ELECTRONIC MATRIX COMMUTATOR Theodore L. Buley, Poughkeepsie, N. Y., assignor to International Business Machines Corporation, New York, N. Y., a corporation of New York Application March 30, 1953, Serial No. 345,651

12 Claims. (Cl. Z50- 27) This invention relates to electronic commutators and more particularly to a commutator employing inexpensive elements as one component thereof to provide a compact unit adapted to produce sequentially timed electrical output voltages.

Previous commutators of the prior art have produced sequentially timed pulses by using a series of gas tube trigger elements separated into two rings jointly controlling hard multigrid electronic tube switches to thereby produce a compact commutator. Such devices have been subject to the slow speed and temperamental operation of gas tube rings and the expensive construction of multigrid switching elements.

The principal object of the present invention is, therefore, to provide an electronic commutator employing high speed hard tube triggering elements and extremely low cost switch elements comprising diodes, which per se, have no grid controls.

Another object is to provide an electronic commutator system comprising a horizontal ring of hard tube triggers which acts upon a complete ring operation to step one element of a similar vertical ring. The rings jointly condition diodes, in a desired pattern, to provide a fast acting and relatively inexpensive commutator or simulated ring of two dimensions which can be compactly associated with the elements of an accounting device.

Other objects of the invention will be pointed out in the following description and claims, and illustrated in the accompanying drawings, which disclose by way of example, the principle of the invention and the best mode which has been contemplated of applying that principle.

ln the drawings:

Fig. l is a combined block and detailed. circuit di agram of a circuit embodying the preferred form of the invention.

Fig. 2 is a detailed circuit diagram and the block representation of an electronic trigger employed in the invention.

Fig. 3 is a detailed circuit diagram and the block representation of another electronic trigger employed in the invention.

Figs. 4 and 5 are detailed circuit diagrams and the block representations of cathode followers employed in the invention.

Wherever shown, unless otherwise indicated in the drawings, the values for the various resistors and condensers are in thousands of ohms and micromicrofarads respectively. For example, a resistor labeled 200 indicates a 200K (200 thousand) ohm resistor; a condenser labeled 100 indicates a 100 micro-microfarad condenser..

A resistor labeled l Meg indicates a l million ohm resistor. The terms positive and negative potentials,

ICC

2. respective elements such as triggers and cathode followers and including the electrical constants will be given.

In Fig. 2, there'is shown one type of electronic trigger whose block symbol is labeled TR-4 and is known in the art as an Eccles-Jordan trigger. The trigger includes 21,616 tube having two triodes, with plate P1 of one triode coupled by a 200K ohm resistor in series with a 1K ohm resistor to the grid G2 of the other triode and platel P2 of theA latter triode coupledl to grid G1 of the rst triode by a 200K ohm resistor in series with.v a 1K ohm resistor. Each of the 200K ohm resistors is shunted by a 100 micro-microfaradl condenser. Grid, G1 is normally negatively biased by a -10Q volty battery 1,0 applied through a reset contact 11, a 200K Ohm resistor and the 1K ohm resistor. Grid G2` is biased by a .100 volt source 12 applied through a 200K ohm resistor and the 1K ohm resistor.

The plate circuit of P1 comprises two resistorsl in series., one of 12K ohms adjacent the plate, and the other of 7.5K ohms connected to a +150 volt source 13. The plate P2 is similarly connected tothe +15() volt source through a 12K and a 7.5K ohm resistor in` series. A terminal 8 which is connected between, the 7.5K ohm and the 12K ohm resistors, provides a tap, in, the plate resistance of the plate P2. A terminal 7 is'. directly connected to the plate P2. the dual triodev are grounded at 14.

As is now well known, when the left hand. Side Of` the tube is rendered conductive, the voltage at4 the plate P1 is lowered from approximately 171,40 volts to applQXimately +40 volts, which, through the coupling previously described, maintains the grid G2 relatiifely negative so that the right hand sideof the tube` is blocked whileI the left hand side conducts, thus making. P1. negative and P2 positive, This is one. state of stability of the trigger and will hereinafter be designated as, the on condition. ln a similar manner, if the iight hand side of the tube is rendered conductive, the reduction in voltage on the plate P2 isapplied by the coupling connection previously described, tothe grid G1 to block the left hand side of the tube, whereupon P1 becomes positive and P2 becomes negative. This. willv be. designated as the oli condition of the trigger.

If, for example, the right hand side. of the tube, is conducting (trigger ol), and a, negative 'voltage is applied to the grid G2, the trigger will` be. lippdl on by blocking thev right hand side and rendering the left hand side conductive. This negative voltageA ifsv applied to grid G2 via a terminal 3, a 40 micro-microfaradccndenser and the 1K ohm resistor.

Likewise, if the left hand side is` conducting (trigger on), and a negative voltage is applied to vgrid G1I via a terminal', a 40 micro-microfarad condenser and the 1K ohm resistor, the left hand side of thetube is `blocked and thev trigger is flipped oli l If a sufficiently positive voltage is, applied, to G1, the left hand side of the tube can be caused to4 conduct. This, method is used` for resetting the trigger and isy performed -by opening the reset contact 11, thus effectively removing the negative bias, voltage from the left4 hand grid andv leaving grid-G1 connectedV through the 1K and 200K'. ohm resistors to P2. which is always positive. Thus, with the left handV side previously non-conducting,

it will. start conducting asA soon as the reset contact opens.

This. operation is known as resetting the trigger 0a.

While specific tube types and values ofy resistors and condensers` have been described in connection with the trigger 'IR-4, theseV are to be taken, asv exemplary only, and the tube types and values may be varied those skilled in the art Without departing from the spirit of the invention.

Fig. 3' illustrates another form of trigger whose block lPainted May s, s

The cathodes K1 and K2 of f hand inputs of all the triggers. pulse turns off the first trigger 21A which, as stated,

3 symbol is labeled TR-l. trigger TR-4 except that it is reset off instead of 011. This is accomplished hy opening a reset contact 1S which effectively removes a -100 volt bias voltage 16 from the right hand grid G2 and leaves G2 connected, through the 1K and 200K ohm resistors to P1 which is always positive. Thus, if the right hand side has not been previously conducting, it will start as soon as the reset contact opens.

In Fig. 4, there is shown a cathode follower whose block symbol is labeled C11-4, and consists of a circuit including one triode of a dual triode 12AV7 type tube. A cathode follower may be defined as a vacuum tube `circuit in which the input signal is applied between the control grid and ground, and the output is taken from between the cathode and ground. The cathode follower has a high input impedance but, on the other hand, has a low output impedance and is capable of producing a power gain. A voltage may be applied to the left hand side of the tube via terminal 7, across a 1 megohm grounded resistor and via a 0.15K ohm resistor to the grid G1.

. The plate P1 is directly connected to a +300 volt source 18. The cathode output is developed across two 4.7K ohm resistors in series between the cathode K1 and ground and taken olf through terminal 8 directly connected to the cathode K1.

In Fig. is shown another cathode follower whose block symbol is labeled CF-2. This is a duplicate of the cathode follower CF-4 except that a terminal 6 is connected between the two 4.7K ohm resistors in the cathode circuit at the right hand side of the tube.

Basically, the circuit shown in Fig. 1 consists of two electronic commutators or rings (of the type shown in the Overbeck Patent No. 2,404,918) composed of triode triggers as shown in Figs. 2 and 3; these rings controlling a diode matrix. One of the rings consists of a horizontal -row of triggers 21A, 21B to 21X, only one of which is on` at any given time. Upon simultaneous application Vof a pulse to eachl of the triggers in the ring, the stage 'to emit an output pulse for advancing the other ring which consists of a vertical row of triggers 91A, 91B to 91X. Thus, for every series of pulses which produces This trigger is identical to one complete operation of the horizontal ring, the vertical ring will advance one step.

In the horizontal ring, the trigger 21A is a type 'TR-4 (Fig. 2) and all the others are type TR-l (Fig. 3) so that, as stated above, trigger 21A will be reset on while all the others will be reset off Leads 31A, 31B to 31M,.

respectively, connect the tapped output terminals 8 of each of the triggers to the respective right hand input of the succeeding trigger stage, and lead 38 closes the ring by connecting the tapped output terminal 8 of the last trigger 21M, to the right hand input of trigger 21A. An input lead 40 from a source of negative pulses is connected through leads 41A, 41B and 41M to all the left The first negative input has been reset on, but the pulse does not affect any of the other triggers which have been reset off. When trigger 21A goes offj its plate P2 (Fig. 2) vgoes negative, as previously described, and this negative swing is applied to the input terminal 3 of the trigger 21B to turn the latter on in a manner previously described.

put terminals 7 of each of the triggers 21A21B, 21M

`terminals of cathode followers 61A, 61B and 61M are conductors 71A, 71B and 71M respectively.

When trigger 21A goes m1, its terminal 7 goes positive and stand-s at approximately +140 volts which is applied to the input of the cathode follower 61A to increase its power output. The cathode output terminal of cathode follower 61A also shifts to +150 volts, which is applied to the vertical matrix lead 71A. As the triggers 21A to 21M advance, there is a sequential application of +140 volts to the vertical matrix leads 71A to 71M.

When the last trigger 21M is on and the +140 volt output is applied to the cathode follower 61M, the tapped output terminal 6 of this cathode follower stands at +70 volts. The next negative pulse applied to the horizontal ring flips the last trigger 21M o so that the voltage at its terminal 7 goes negative (+40 volts). This voltage applied to the cathode follower 61M causes its output terminal 6 to go to +20 volts. The negative swing of 50 volts is applied to the trigger 91A of the vertical ring and advances this ring one step, as will now be desucceeding stage, while lead closes the ring, by connecting the tapped output terminal 8 of the bottom trigger to the right hand input of the top trigger. This vertical electronic ring is advanced once for each complete cycle of the horizontal ring.

Leads 121A, 121B and 121N connect the output terminals 7 of the triggers 91A, 9th and 91N to the input terminals of cathode followers 131A, 131B and 131N which are of type (1F-4. The output terminals of the cathode followers are connected to horizontal matrix leads 151A, 151B and 151N.

When one of the triggers 91A, 91B or 91N goes on,

. its output terminal 7 goes positive and stands at approximately volts which is applied to its associated cathode follower 131A, 131B and 131N. The follower, in turn, applies +140 volts to its associated horizontal matrix lead 151A to 1S1N. Thus, it is evident that there is a 4sequential application of +140 volts to the horizontal matrix leads, and this application takes place only once for each complete operation of the horizontal ring. Connected between each of the vertical matrix leads '71A, 71B, 71M and the horizontal matrix leads 151A,

151B, 151N is a diode 161. The diode circuits shown in this invention comprise simple and inexpensive means for producing a timed electrical output only when there is a coincidence of two positive contro-l voltages. Such diode circuits, which are designed for giving an output only when there is a conjunction of two similar control voltages, are known as gating or And circuits. The

diode circuits shown are merely by way of illustration and may be replaced by other diode And circuits well 65 -vention, and as is deemed obvious with the state of the art, the electronic diodes may be replaced by crystal known in the art without changing the scope of the indiodes.

Since the diode circuits shown in Fig. l are all the same, only one will be described in detail and it will be ,understood that they all operate in a similar marmer.

Considering the diode circuit between the vertical matrix lead 71A and the horizontal matrix lead 151A, the cathode of diode 161 is tied to the vertical matrix lead '71A -and its plate is connected through a 15K ohm resistor 'to the horizontal' matrix lead 151A. Between the plate of diode 161 and the 15K ohm resistor is connected an output terminal 201A. As previously stated, the voltage on vertical matrix lead 71A varies from +140 volts when trigger 21A is on to +40 volts when trigger 21A is ofi The voltage on the horizontal lmatrix lead 151A varies in the same way, with the flipping of trigger 91A. It will now be shown that output terminal 201A will go positive (+140 volts) only when both trigger 21A and trigger 91A are on thus supplying +140 volts to both of the leads 71A and 151A, respectively.

There are four possible conditions to be considered.

(l) Both the vertical matrix lead 71A and the horizontal matrix lead 151A are at +40 volts. Since there is no voltage difference across the diode 161, it will not conduct and there will be no voltage drop across the K ohm resistor so that the voltage at the terminal 201A will be equal to the voltage at the horizontal matrix lead 151A, namely, +40 volts. j

(2) The vertical matrix lead 71A is at +140 volts and the horizontal matrix lead is at +40 volts. In this case, since the plate of the diode 161 is negative with respect to the cathode, there will be no conduction, and once again the terminal 201A will be at the same voltage as the horizontal matrix lead 151A, which is +40 volts.

(3) The vertical matrix lead 71A is at +40 volts and the horizontal matrix lead 151A at +140 volts. In this case, there will be conduction through the diode and a voltage drop across both the diode 161 and the 15K resistor. However, since the voltage drop across the diode, when conducting, is very small, compared to that across the 15K resistor, the diode can be effectively considered as a short circuit and the terminal 201A will be effectively at the voltage level of the vertical matrix lead 71A, which is +40 volts. l

(4) The fourth condition is the only condition in which both trigger 21A and trigger 91A are on. In this case, the vertical matrix lead 71A and the horizontal matrix lead 151A are both at +140 volts. Since there is no potential difference across the diode 161, there will be no conduction, and the voltage at the terminal 201A will be the voltage at the horizontal matrix lead 151A, which is +140 volts. Thus, this fourth condition is the only one in which the terminal 201A goes positive, which is the result desired.

Assuming that trigger 91A is on, each input pulse to the horizontal ring will be instrumental in producing sequentially positive pulses at the terminal outputs 201A through 201M, respectively, which, as is now obvious, are the terminals associated with horizontal matrix lead 151A and each of the vertical matrix leads 71A to 71M.

Terminals 202A to 202M are similarly associated with the horizontal matrix lead 151B and eachof the vertical matrix leads 71A to 71M respectively.

An output pulse produced upon completion of one full operation of the horizontal ring, turns ofi trigger 91A and iiips trigger 91B on to thus place +140 volts on the horizontal matrix lead 151B. Thus as the horizontal ring steps through its various stages, positive pulses will appear sequentially at terminals 202A to 202M.

Each operation of the horizontal ring continues the above described method of operation until the last terminal is pulsed positive. The next input pulse to the horizontal ring will then start the operation all over again, trigger 91A being turned on to condition the horizontal matrix lead 151A and the stepping of the horizontal ring applying proper conditioning potentials to the respective vertical matrix leads 71A to 71M whereby, as described above, positive outputs are obtained at terminals.

it has thus been shown how two hard tube trigger rings can act conjointly to condition a diode matrix to provide a fast acting and relatively inexpensive commutator. It will be understood that by this invention, the lnumber of output terminals in the matrix increases in 'proportion-to the product of the numbers of triggers in the ring circuits. On account of this, the expense involved in constructing the commutator increases much less than the increase in output terminals.

While there have been shown and described and pointed out the fundamental novel features of the invention as applied to a preferred embodiment, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art, without departing from the spirit of the invention. It is the intention, therefore, to be limited only as indicated by the scope of the following claims.

What is claimed is:

l. An electronic commutator comprising, in combination` a rst ring of M hard tube type cross coupled triode trigger stages, means initiating sequential individual operations of said M triggers in said first ring, a second ring of N hard tube type cross coupled triode trigger stages, means connecting one of said M triggers in said first ring to said second ring to initiate sequential individual operations of said N triggers in said second ring after each complete cycle of operation of said first ring, cathode followers associated with said triggers in each of said rings, means connecting each of said triggers in each of said rings to the input of its associated cathode follower, said connecting means being operative to selectively activate said associated cathode' follower upon the sequential operation of' said triggers in each of said rings, a two dimensional vdiode matrix comprising a plurality of diodes arranged in' M columns of N rows, a plurality of resistors, each of which is connected at one end to one electrode of each of 'said diodes, first leads individually connected to the other electrode of each of said diodes along individual columns, second leads individually connected to the other end of each of said resistors along individual rows, means connecting said first leads to the output of said cathode followers associated with eachv of the M triggers of said first ring, means connecting said second leads to the output of said cathode followers associated with each of the N triggers of said second ring, and output terminals connected between each of said resistors and said diodes, said output terminals being rendered operative in the matrix pattern controlled by the relative sequential activations of said cathode followers.

2. An electronic commutator comprising, in combination, a first ring of M hard tube type triode trigger stages, means initiating sequential individual operations of said M triggers in said first ring, a second ring of N hard tube type triode trigger stages, means connecting one of said M triggers in said first ring to said second ringto initiate sequential individual operations of said N triggers in said second ring after each complete cycle of operation of said first ring, a two dimensional diode matrix comprising a plurality of diodes arranged in M columns of N rows, a plurality of resistors each of which is connected at one end to one electrode of eachof said diodes, rst leads individually connected to the other electrodeof each of said diodes along individual columns, second leads individually connected to the other end of each of said resistors along individual rows, means connecting each of said first leads to an associated trigger of said first ring, said connecting means being selectively operative to energize said associated first leads upon the sequential operation of said triggers in said rst ring, means coitnecting each of said second leads to an associated trigger of said second ring, said connecting means being selec'- tively operative to energize said associated second leads upon the sequential operation of said triggers in said secondring, and output terminals connected between each of said resistors and said diodes, said output terminals being rendered operative in the matrix pattern controllediby the coincidence of the energizations of said first and second leads;

3. An electronic commutator comprising in combination, a iirst ring of M hard tube type triode trigger stages, means initiating sequential individual operations of said M triggers in said lirst ring, a second ring of N hard tube type triode trigger stages, means connecting one of said M triggers in said'iirst ring to said second ring to initiate sequential individual operations of said N triggers in said second ring after each compiete cycle of operation of said first ring, a two dimensional diode matrix comprising a plurality of diodes arranged in M columns of N rows, a plurality of resistors each of which is connected at one end to one electrode oi each of said diodes, fust leads individually connected to the other end of each of said resistors along individual columns, second leads individually connected to the other electrode of each of said diodes along individual rows, means connecting each of said rst leads to an associated trigger of said iirst ring, said connecting means being selectively operative to energize said associated iirst leads upon the sequential operation of said triggers in said tirst ring, means connecting each of said second leads to an associated trigger of said second ring, said connecting means being selectively operative to energize said associated second leads upon the sequential operation of said triggers in said second ring, and output terminals connected between each of said resistors and said diodes, said output terminals being rendered operative in the matrix pattern controlled by the coincidence of the energizations of said rst and second leads. v

4. An electronic commutator comprising, in combination, a irst ring of hard tube type triode triggers, means initiating sequential individual operations of said triode triggers in said iirst ring, a second series of hard tube type triode triggers, means connecting said iirst ring to said second series to initiate sequential individual operations of said triode triggers in said second series, a two-dimensional matrix composed of a plurality of diode And circuits arranged in columns and rows corresponding to the triggers in said ring and series, each diode And circuit having an output terminal, means connecting each trigger in said iirst ring to one of the inputs of the diode And circuits in the corresponding column of one dimension of said matrix, and means connecting each trigger in said second series to the other input of said diode And circuits in the corresponding row of a second dimension of said matrix whereby said output terminals are rendered operative in a pattern controlled by the relative sequential individual operations of said lirst ring and said second series.

5. An electronic commutator comprising, in combination, a first ring of hard tube type triode triggers, means initiating sequential individual operations of said triode triggers in said tirst ring, a second series of hard tube type triode triggers, means connecting said iirst ring to said second series and initiating sequential individual operations of said triode triggers in said second series, a two dimensional matrix composed of a plurality of diodes and resistors arranged in columns and rows corresponding to the triggers in said ring and series, each diode coupled to one of said resistors, means connecting each trigger in said iirst ring to the uncoupled inputs of the diodes in the corresponding column of one dimension of said matrix, means connecting each trigger in said second series to the uncoupled ends of the resistors in the corresponding row of a second dimension of said matrix, and an output terminalconnected between each of said resistors and associated diode, said output terminals being rendered operable in a pattern controlled by the relative sequential individual operations of said iirst ring and said second series.

6. An electronic commutator comprising, in combination, a rst ring of hard tube type triode triggers, means initiating sequential individual operations of said triode triggers in said first ring, a second series of hard tube type triode triggers, means connecting said rst ring to said second series and initiating sequential individual operations of said triode triggers in said second series, a two dimensional matrix composed of a plurality of diodes and resistors arranged in columns and rows corresponding to the triggers in said ring and series, the anode of each diode coupled to one of said resistors, means connecting each trigger in said lirst ring to the cathodes of the diodes in the corresponding column of one dimension of said matrix, means connecting each trigger in said second series to the uncoupled ends of said resistors in the corresponding row of a second dimension of said matrix, and an output terminal connected between each of said resistors and associated diode, said output terminals being rendered operable in a pattern controlled by the relative sequential individual operations of said first ring and said second series.

7. An electronic commutator comprising, in combination, first and second rings of hard tube type triode triggers, a two dimensional matrix composed of a plurality of diode And circuits arranged in columns and rows corresponding to the triggers in said rings, each diode And circuit having an output terminal independent from all said other diode And circuit output terminals, means initiating sequential individual operations of cach of said rings of triggers, means connecting each trigger in said first ring to one of the inputs of the diode And circuits in the corresponding column of one dimension of said matrix, and means connecting each trigger in said second series to the other input of said diode And circuits in the corresponding row of a second dimension of said matrix whereby said independent output terminals are rendered operable in a pattern controlled by the relative sequential individual operations of said lirst and second rings.

8. An electronic commutator comprising, in combination, iirst and second rings ot hard tube type triode triggers, a two dimensional .matrix composed of a plurality of diodes and resistors arranged in columns and rows corresponding to the triggers in said rings, each diode connected in series to one of said resistors, means initiating sequentially individual operations of each of said rings of triggers, means connecting each trigger in said first ring to the unconnected inputs of the diodes in the corresponding column of one dimension of said matrix, means connecting such trigger in said second ring to the unconnected inputs of said resistors in the corresponding row of a second dimension of said matrix, and an output terminal connected between each of said resistors and associated diode, said output terminals being rendered operable in a pattern controlled by the relative sequential individual operations of said rst and second rings.

9. An electronic commutator comprising, in combination, irst and second rings of hard tube type triode triggers, a two dimensional matrix composed of a plurality of diodes and resistors arranged in columns and rows corresponding to the triggers in said rings, the anode of each diode coupled to one of said resistors, means initiating sequential individual operations of each of said rings of triggers, means connecting each trigger in said first ring to the cathodes of the diodes in the corresponding column of one dimension of said matrix, means connecting each trigger in said second ring to the unconnected inputs of said resistors in the corresponding row o a second dimension oi said matrix, and an output terminal connected at the coupling between each of said resistors and the anode of said diodes, said output terminals being rendered operable in a pattern controlled by the relative sequential individual operations of said 'lirst and second rings.

it). An electronic commutator comprising, in combination, tirst and second rings of hard tube type triode triggers, a two dimensional matrix composed of a plurality of diodes and resistors arranged in columns and rows corresponding to the triggers in said rings, an electrode of each diode coupled to one of said resistors, means initiating sequential individual operations of each of said rings of triggers, means connecting each trigger in said rst ring to the other electrodes of the diodes in the corresponding column of one dimension of said matrix, means connecting each trigger in said second ring to the unconnected inputs of said resistors in the corresponding row of the second dimension of said matrix, and an output terminal connected at the coupling between each of said resistors and the associated electrodes of said diodes, said output terminals being rendered operable in a pattern controlled by the relative sequential individual operations of said rst and second rings.

11. An electronic commutator comprising a plurality of bistable device rings, each comprising a plurality of elements, a two-dimension matrix of conductors arranged in columns and rows corresponding to the elements in said rings, said rings producing a stepping pattern of voltages applied to the two-dimensions of the matrix of conductors to thereby establish a matrix pattern, and means comprising diode gating circuits respectively controlled by the voltages from the conductors in the corresponding columns of one ring and by the voltages fromthe conductors in the corresponding rows of the other ring, said diode gating circuits comprising elements of said matrix, cach diode gating circuit having an output terminal independent from all said other diode And circuit output terminals, said independent output terminals being rendered operative in the matrix pattern developed by said conductors.

12. An electronic commutator comprising a plurality of electron valve rings each comprising a plurality of elements, a two dimensional matrix of conductors arranged in columns and rows corresponding to the elements in said rings, said rings producing a stepping pattern of voltages applied to the two dimensions ofthe matrix of conductors to thereby establish a matrix pattern, and means comprising diodes respectively controlled by the voltages from the conductors in the corresponding columns of one ring and by the voltages from the conductors in the corresponding rows of the other ring, said diode means comprising ele- .ments of said matrix, each said diode means including one resistor connected to each of said diodes, and output terminals connected between each of said resistors and said diodes, said output terminals being rendered operative in the matrix pattern developed by said conductors.

References Cited in the le of this patent UNITED STATES PATENTS 2,049,763 DeForest Aug. 4, 1936 2,136,441 Karolus Nov. 15, 1938 2,195,864 Knoop Apr. 2, 1940 2,308,778 Prince Ian, 19, 1943 2,443,198 Sallach June 15, 1948 2,465,355 Cook Mar. 29, 1949 2,686,299 Eckert Aug. 10, 1954

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