US2841748A - Relay circuit - Google Patents

Description

July 1, 1958 A. c. REYNOLDS, JR 2,841,748

I RELAY CIRCUIT Filed Dec. 15, 1954 5 Sheets-Sheet 2 D E SE L .L AB

40 E2 0 B A 00 FIG 20 l EWJCE m 1N VENTOR Andrew C Reyna/41 s Jr BY 15 E, /W

ATTORNEY July 1, 1958 A. c. REYNOLDS, JR 2,841,748

RELAY CIRCUIT Fiiled Dec. 15, 1954 s Sheets-Sheet s 94 Z 2 BC A P E, 6 5 %AE b B3A:5 BE A66 D1 7 A3 IF? 9s LZBJABD AGE 96 91 87 B2 \L E2 i 0 05 A95 B 0 E 1 0 co ABF:

- 99 a9 c E3 DE Ac ga INVENTOR A flQ e C Reyna/0'5 Jr.

ATTORNEY RELAY CIRCUIT Andrew C. Reynolds, In, Endicott, N. Y., assignor to Internationai Business Machines Corporation, New York, N. ii, a corporation of New York Application December 15, 1954, Serial No. 47 5,520

10 Claims. (Cl. 317-137) This invention relates to distribution networks and more particularly to an improved relay circuit arrangement adapted for economical inclusion in relay distribution networks.

Recent years have witnessed an almost phenomenal expansion in the utilization of electrical relays in electrical apparatus of various types such as, for example, electrical data processing machines and automatic telephonic switching apparatus. Apparatus and machinery of this type frequently include complex electrical circuits and networks utilizing great numbers of relays, oftentimes running into the hundreds or thousands or more. In such complex circuits and networks it is highly desirable from both an economic and operating standpoint that the most efficient and economical use of relays be made, and the present invention is directed towards that end.

Electrical relays, particularly of the wire contact type, are economically obtained in the so-called standard sizes. Certain of the standard sizes are the 4, 6 and 12 element units wherein each element consists of a transfer assembly composed of a normally open con tact, a normally closed contact and a transfer contact actuated by the relay armature. In the design of electrical equipment incorporating a multiplicity of relay elements, it is of appreciable commercial importance to satisfy the specific circuit conditions in such a manner as to achieve maximum economy with respect to space utilization and relay costs. The desired economies are perhaps best eifected through obtaining of a uniform distribution of the utilization of relay contacts. However, such uniform distribution of utilization of relay contacts by circuitry heretofore known has not been obtainable in many types of important and widely used relay networks. One method heretofore used by the art to obtain the desired end of greater uniformity of relay contact distribution is by utilization of spring pile ups. However, such a procedure only shifts the location of the problem as it creates special problems in magnet and armature design due to the consequent unequal spring loading.

This invention may be briefly described as an improved relay circuit for the so-called two out of five self-checking code wherein maximum economy is achieved through the utilization of only five four-element relay units in circuits not requiring hold points for information storage, or through the utilization of only five six-element relay units in circuits wherein hold points are required for information and data storage. Included in the particular relay circuit arrangements for the two out of five selfchecking code is a novel relay subcircuit which permits the desired economical distribution of relay contacts and is of utility either alone or as a component element in other more complex relay distribution networks.

Although the invention finds particular utility in relay networks and will be described in conjunction therewith, the principles set forth herein are equally applicable to other types of switching mechanisms such as multivibrators, clutching arrangements and so forth.

2,841,748 Patented July 1, 1958 An object of this invention is the provision of an improved relay circuit arrangement for relay distribution networks.

Another object of this invention is the provision of an improved circuit arrangement for distribution networks.

Other objects and advantages of the invention will be pointed out in the following description and claims and illustrated in the accompanying drawings which describe, by way of example, the principles underlying the invention and the presently preferred embodiments of the relay circuit arrangements employing those principles.

Referring to the drawings:

Fig. 1 shows the basic tree circuit for the two out of five self-checking code;

Fig. 2 is a schematic representation of the improved relay circuit for the two out of five self-checking code with complete back circuit elimination;

Fig. 2A is a relay circuit diagram of the schematic circuit illustrated in Fig. 2;

Fig. 3A is an improved subcircuit for producing three of the possible eight switching functions of three variables;

Fig. 3B is an alternative form of the circuit as set forth in Fig. 3A;

Fig. 4 is a schematic representation of the improved relay circuit for the two out of five code without provision for complete back circuit elimination; and

Fig. 4A is a relay circuit diagram of the schematic circuit illustrated in Fig. 4.

The principles of the invention herein disclosed are conveniently explained in conjunction with a relay network rather than other types of switching devices and particularly with reference of a particular relay distribution network for transmitting numeric information in the socalled two out of five self-checking code.

The two out of five self-checking code, as embodied in a relay distribution network, requires the provision of ten distinct electrical paths, involving transfers on each of five relay units for the selective transmission of a signal. Each path may be conveniently considered as representative of a. decimal digit in the range 0-9. In such a system the closure of any particular path is dependent upon operation of two and only two of the five relays, with the remaining three relays remaining unoperated. Self-checking of the system is assured by arranging the circuit so that operation of any one relay by itself leaves all of the output paths open and in a similar manner arranging the circuit so that operation of three or more relays also opens all paths through the network. In addition to the above requirements, an additional requirement is usually imposed upon a distribution network for the two out of five self-checking code which is that under no conditions or combinations of operated and unoperated relays will any two or more of the ten output terminals be connected by a closed path internal to the distribution network. This latter requirement may be more simply stated by asserting that the distribution network must be free of back circuits.

In commercial design, units readily available for designing a circuit having the above properties are conventional Wire contact relays. As mentioned above wire contact relays are constructed in three standard sizes of 4, 6 and 12 elements respectively. Each element consists of a transfer assembly composed of a normally open contact (hereinafter designated as N/O), a normally closed contact (hereinafter designated as N/C), and a transfer contact adapted to be actuated by the relay armature.

As a matter of convenience, the five relays constituting the network for the two out of five code will be identified by the letters A, B, C, D and E, with the particular transfer element thereof being identified by a numerical subscript. A normally open (N/O) point on a relay will be symbolized by the appropriate capital letter 'dD-E lt |r l l l w bdlbdlbdlbdbd w tdltzdlbdl olo ol olo OIQIO elelo elolo ole mlealrelm unmet mm Fig. 1 shows the conventional basic tree circuit which meets the circuit specifications as set forth in the above permutation table. In this circuit there is provided a single input locality and ten separate output localities 11 through 20 inclusive. The first path through the network is disposed intermediate the input locality 10 and the first output locality 11 and, as illustrated, includes contacts 781, E, 6 D and E. In a similar manner the remaining nine paths through the network are identified by the letter coding disposed adjacent the respective output terminals and which corresponds to the permutation tabulation above set forth. In the illustrated conventional tree circuit it should be noted that the distribution of relay transfers is as follows: A1, B2, C4, D-7 and E-lO. Such distribution is decidedly unbalanced, and is not economically compatible with the readily available standard sizes of wire contact relays, i. e. the 4, 6 and 12 element units. Construction of such a network utilizing standard size relays results in unavoidable wastage of relay contacts unless certain of the unused contacts can be utilized for other purposes within the particular machine or apparatus in which the network is included. As discussed above, a more uniform distribution of contacts can be effected by the utilization of spring pile ups. However, such eXpedients present other problems in the form of specially designed armatures and magnets in order to accommodate the unequal spring loading.

The improved circuit is illustrated schematically in Fig. 2 and in a conventional relay circuit diagram in Fig. 2A. With reference of Figs. 2 and 2A there is provided a relay network having a single input terminal 3% and ten separate output terminals 31 through 40, respectively. There is provided a first subcircuit connecting the input terminal 30 to a first junction point 41 through A E The first circuit is paralleled by a second subcircuit connecting the i nput locality 30 to the first junction point 41 through A B The first junction point 41 is connected to a cogd junction point 42 by a third subcircuit through D E paralleled by a fourth subcircuit through 6 The second junction point 42 is connected to a third junction point 43 by a fifth subcircuit through C The third junction point 43 is connected to the first output terminal 31 by a first output circuit through X and to the second Zutput terminal 32 by a second output circuit through 2. Connected intermediate 1 3 and E in the third sub- Glrcuit and a fourth junction point 4 4is a sixth subcircuit 4 through 6 The fourth junction point 44 is connected to a fifth junction point 45 by a seventh subcircuit through E The fifth junction point 45 is connected to the third output terminal 33 by a third output circuit through A and to the fourth output terminal 34 by a fourth output circuit through A The fourth junction point 44 is connected to a sixth junction point 46 by an eighth subcircuit through E; D The sixth junction point 46 is connected to the fifth output terminal 35 by a fifth output circuit through A; and to the sixth output terminal 36 by a sixth output circuit through A Connected intermediate A and B in the second subcircuit and a seventh junction point 47 is a ninth subcircuit including 13;. The seventh junction point 47 is connected to an eighth junction point 48 by tenth subcircuit through D and E paralleled by an eleventh subcircuit through C The eighth junction point 48 is connected to the seventh output terminal 37 by a seventh output circuit through C and D Connected intermediate D and E in the tenth subcircuit and a ninth junction point 49 is a twelfth subcircuit through D The ninth junction point 49 is connected to the eighth output terminal 38 by an eighth output circuit through B and E and to the ninth output terminal 39 by a ninth output circuit through B Also connected intermediate D and E in the tenth subcircuit and a tenth junction point 50 is a thirteenth subcircuit through E The tenth junction point 50 is also connected intermediate A and B in the first subcircuit by a fourteenth circuit including B and C The tenth junction point 50 is connected to the tenth output locality 40 by a tenth output circuit through C and B In the above described network the first path therethrough and connecting the input terminal 30 with the first output terminal 31 includes a circuit traceable through A B D B C and A This circuit is completed by actuation of relays B and C as indicated by the coding adjacent the output terminals and which corresponds to the permutation table for the two out of five code as set forth above. The following table sets forth in a convenient form the relay elements included in the above described first path and the other nine separate paths traceable through the network.

Output Path No. Relay Elements Terminal 31 K1315 13 0 K: 32 A1 3 2 1 t 1 B 33 K1 Br 1 6 E3 K: 34 A E: 5 62 E3 A3 35 K1 B161 E 63 E D 36 A1 fin 61 3 3 1 62 E D; A;

The above described relay circuit has a balanced distribution as follows: A-4, B-4, C-4, D-4 and E-4 and is thought to be the most economical circuit possible for the prescribed conditions for the two out of fiveself-checle ing code with complete back circuit elimination. As illustrated above, where storage is not required, five fourelement relays are all that are necessary for the complete circuit. If storage is required five six-element relays are required in order that a necessary hold point may be provided. With the exception of the hold point wire, the cabling is precisely the same for both applications as would be readily apparent to one skilled in this art.

The circuit illustrated in Figs. 2 and 2A is a completely safe circuit for use in that no conditions of operation either correct or incorrect can create a back circuit or a Sneak path connecting any two of the ten output terminals together internally of the network.

The obtaining of uniform distribution in a relay network of the type described is largely dependent upon a so called triad or triangular bridge circuit which is included as a component element thereof. This triad or triangular bridge circuit may be considered as a building block type of unit which has utility taken alone or as a component element in a more complicated relay network.

An embodiment of one such triad circuit is illustrated in Fig. 3A. In this embodiment there is provided an input terminal 6i) and three output terminals 6]., 62 and 63 respectively. The embodiment illustrated in Fig. 3A is for a two out of three code in which the relay permutations are as follows:

i l l eelwee OOlO There is provided a triangular bridge circuit 64 of three relay contacts A B and C with the input terminal 68 connected thereto intermediate A and B. The first output terminal 61 is connected to the triangular bridge 64* intermediate A and C through A. The second output terminal 62 is connected to the triangular bridge 64 intermediate B and C through E and an A. The third output terminal 63 is also connected to the triangular bridge at intermediate B and C but is connected thereto through As the above described triad circuit illustrated in Fig. 3A is constituted, there will he a selective output in response to actuation of two out of the three relays as indicated in the coding at the right of the figure and which corresponds to the permutation chart set forth above. For example, the first path through the network intermediate the input terminal and the first output terminal 61 is completed by actuation of relays B and C. This results in closure of the B and C contacts which together with A form a single path through the unit. The other two paths through the network and terminating in the second and third output terminals 62 and 63 are completed in a similar manner and in accordance with the indicated coding.

Fig. 3B is an alternative form of the circuit illustrated in Fig. 3A. In this embodiment the starting condition of the individual relay contacts is reversed from that of Fig. 3A, and the circuit is thereby selectively responsive to actuation of any one of the three relays constituting the triad. As illustrated in the drawings, there is provided an input terminal 70 and three separate output terminals 71, 72 and 73. As was the case with the circuit of Fig. 3A, there is provided a triangular bridge circuit 7 5 of the three contacts A g and C, withihe input terminal connected thereto intermediate A and B. The first output terminal 71 is connected to the bridge 74 intermediate A and C through A. The second output terminal 72 is connected to the bridge 7 intermediate and C through C and an The third output terminal 73 is connected to the bridge '74 intermediate B and C through E.

The circ it illustrated in 3B is responsive to actuation of a single relay as indicated in the coding at the right of tnefigure. For example, the first path through the network intermediate the input terminal 7% and the first output terminal 7 is completed by actuation of relay A. The other two paths through the network and terminating at the second and third output terminals 72 and 73 are completed in a similar manner and in accordance with the indicated coding.

In many complex network applications the feature of complete back circuit elimination in a relay network for (i ii 6 handling the two out of five code is not necessary and the additional expense required for obtaining such protection is not warranted. If complete back circuit elimination is not required, a simplified circuit over that illustrated in Figs. 2 and 2A, and described at an earlier point in this specification, can be provided. This simplified circuit results in additional economies in the number of components over the circuit heretofore described and in which complete back circuit elimination was aiforded. This simplified circuit is illustrated schematically in Fig. 4 and in a conventional relay circuit diagram in Fig. 4A.

With reference to Figs. 4 and 4A, there is provided a relay network having a single input terminal 30 and ten separate output terminals 81 through 90 respectively. There is provided a first subcircuit connecting the input terminal 30 to a first junction point 91 through A and B This first subcircuit is paralleled by a second subcircuit connecting the first junction point 91 to the input terminal through A and 5 The first junction point 91 is connected to a second junction point 92 by a third subcircuit through 5 and E paralleled by a fourth subcircuit through C The second junction point 92 is connected to a third junction point 93 by a fifth subcircuit through C The third junction point 93 is connected to the first output locality 31 by a first output circuit through A and to the second output locality 82 by a second output circuit through A Connected intermediate 5 and E in the third subcircuit and a fourth junction point 94 is a sixth subcircuit through E and C The fourth junction point 94 is connected to the third output terminal 83 by a third output circuit through and to the fourth output terminal 84 by a fourth output circuit through B Connected intermediate 5 and E in the third subcircuit and a fifth junction point 95 is a seventh subcircuit which includes D The fifth junction point 95 is connected to the fifth output terminal by a fifth output circuit through A and to the sixth output terminal 86 by a sixth output circuit through Z Connected intermediate A and B in the first subcircuit and a sixth junction point 96 is an eighth subcircuit including l The sixth junction point 96 is connected to a seventh junction point 97 by a ninth subcircuit through C and E paralleled by a tenth subcircuit through D The seventh junction point 97 is connected to the seventh output terminal 87 by a seventh output circuit through 15 Connected intermediate C and E2 in the ninth subcircuit and an eighth junction point 98 is an eleventh subcircuit including E The eighth junction point 98 is also connected intermediate A and T31 in the second subcircuit by a twelfth subcircuit through B and The eighth junction point 98 is connected to the eighth output terminal 88 by an eighth output circuit through D Connected intermediate C and E in the ninth circuit 521d a ninth junction point 99 is a thirteenth circuit through C The ninth junction point 99 is connected to the ninth output terminal 89 by a ninth output circuit through E; and to the tenth output terminal by a tenth output circuit through E In the above described network the first path therethrough and connecting the input terminal 80 with the first putput terminal 81 includes a circuit traceable through A B 15 E C and A The circuit is completed by actuation of relays A and C as indicated by the coding adjacent the output terminals and which corresponds to the permutation table for the two out of five code as set forth earlier in this specification. The following table sets forth in a convenient form the relay elements in- 7 cluded in the above described first path and the other nine separate paths traceable through the network.

The circuit set forth in Figs. 4 and 4A is felt to be the most economical circuit possible for the prescribed conditions for the two out of five self-checking code. The circuit has the following balanced distribution: A-3, B-3, C-3, D-3 and E-3, and it should be noted that the network in question requires only three transfers on each of five relays. This leaves a free transfer for a hold point when utilizing a standard 4 transfer relay assembly. The circuit of Figs. 4 and 4A, as was the case with the circuit of Figs. 2 and 2A, is also balanced with respect to spring loading.

In accordance with the provisions of the patent statutes, I have herein described the principle of operation of this invention, together with the elements which I now consider to constitute a workable embodiment thereof, but I desire to have it understood that the structure is only illustrative and that while it is designed to use the various features and elements in the combinations and relations described, some of these may be altered and modified without interfering with the more general results outlined.

Having thus described my invention, I claim:

1. A twenty transfer element relay distribution network for selectively providing ten discrete electrical paths from a common input locality to ten output localities in response to selective actuation of eight transfer elements comprising first, second, third, fourth, and fifth relays, each of said relays having first, second, third and fourth transfer elements, each of said transfer elements including a normally open contact, a normally closed contact and a transfer contact displaceable from engagement with the normally closed contact into engagement with the normally open contact in response to actuation of the relay associated therewith, said transfer elements arranged in electrical circuit with conducting means to provide a first subcircuit connecting an input locality to a first junction point through the normally open contact of the first transfer element of the first relay and the normally closed contact of the second transfer element of the second relay, a second subcircuit connecting said input locality to said first junction point through the normally closed contact of the first transfer element of the first relay and the normally open contact of the first transfer element of the second relay, a third subcircuit connecting said first junction point with a second junction point through the'normally closed contact of the first transfer element of the fourth relay and the normally closed contact of the first transfer element of the fifth relay, a fourth subcircuit connecting said first and second junction points through the normally closed contact of the first transfer element of the third relay, a fifth subcircuit connecting said second junction point with a third junction point through the normally open contact of the first transfer element of the third relay, and a first output circuit connecting said third junction point with a first output locality through the normally closed contact of the second transfer element of the first relay, a second output circuit connecting said third junction point with a second output locality through the normally open contact of the second t 8 transfer element of the first relay, a sixth subcircuit connecting a point intermediate the normally closed contact of the first transfer element of the fourth relay and the normally closed contact of the first transfer element of the fifth relay in the third subcircuit and a fourth junction point through the normally closed contact of the second transfer element of the third relay, a seventh subcircuit connecting said fourth junction point with a fifth junction point through the normally open contact of the third transfer element of the fifth relay, a third output circuit connecting said fifth junction point to a third locality through the normally closed contact of the third transfer element of the first relay, a fourth output circuit connect ing said fifth junction point to a fourth output locality through the normally open contact of the third transfer element of the first relay, an eighth subcircuit connecting said fourth junction point to a sixth junction point through the normally closed contact of the third transfer element of the fifth. relay and the normally open contact of the third transfer element of the fourth relay, a fifth output circuit connecting said sixth junction point to a fifth output locality through the normally closed contact of the fourth transfer element of the first relay, a sixth output circuit connecting said sixth junction point to a sixth output locality through the normally open contact of the fourth transfer element of the first relay, a ninth subcircuit connecting a point intermediate the normally closed contact of the first transfer assembly of the first relay and the normally open contact of the first transfer element of the second relay in the second subcircuit to a seventh junction point through the normally closed contact on the first transfer element of the second relay, a tenth subcircuit connecting said seventh junction point to an eighth junction point through the normally open contact of the second transfer element of the fourth relay and the normally open contact of the second transfer element of the fifth relay, an eleventh subcircuit connecting said seventh junction point with the eighth junction point through the normally open contact of the third transfer element of the third relay, a seventh output circuit connecting said eighth junction point to a seventh output locality through the normally closed contact of the third transfer element of the third relay and the normally open contact of the fourth transfer element of the fourth relay, a twelfth subcircuit connecting a point intermediate the normally open contact of the second transfer element of the fourth relay and the normally open contact on the second transfer element of the fifth relay in the tenth subcircuit with a ninth junction point through the normally closed contact of the second transfer element of the fourth relay, an eighth output circuit connecting said ninth junction point to an eighth output locality through the normally closed contact of the fourth transfer element of the second relay and the normally open contact of the fourth transfer element of the fifth relay, a ninth output circuit connecting said ninth junction point'to a ninth output locality through the normally open contact of the fourth transfer element of the second relay, a thirteenth subcircuit connecting the point intermediate the normally open contact of the second transfer element of the fourth relay and the normally open contact of the second transfer element of the fifth relay in the tenth subcircuit to a tenth junction point through the normally closed contact of the second transfer element of the fifth relay, a fourteenth subcircuit connecting a point intermediate the normally open contact of the first transfer element of the first relay and the normally closed contact of the second transfer element of the second relay in the first subcircuit with said tenth junction point through the normally open contact of the second transfer element of the second relay and the normally closed contact of the fourth transfer element of the third relay, and a tenth output circuit connecting said tenth junction point to a tenth output locality through the normally open contact of the fourth transfer element of the third relay and 9 the normally closed contact of the third transfer element of the second relay.

2. The distribution network as set forth in claim 1 wherein each of said relays has an additional transfer element for holding purposes.

3. A fifteen transfer element relay distribution network for selectively providing ten discrete electrical paths from a common input locality to ten output localities in response to selective actuation of six transfer elements comprising first, second, third, fourth, and fifth relays, each of said relays having first, second and third transfer elements, each of said transfer elements including a normally open contact, a normally closed contact and a transfer contact displaceable from engagement with the normally closed contact into engagement with the normally open contact in response to actuation of the relay associated therewith, said transfer elements arranged in electrical circuit with conducting means to provide a first subcircuit connecting the input locality to a first junction point through the normally closed contact of the first transfer element of the first relay and the normally open contact of the second transfer element of the second relay, a second subcircuit connecting said input locality to said first junction point through the normally open contact of the first transfer element of the first relay and the normally closed contact of the first transfer element of the second relay, a third subcircuit connecting said first junction point with a second junction point through the normally closed contact of the first transfer element of the fourth relay and the normally closed contact of the first transfer element of the fifth relay, a fourth subcircuit connecting said first junction point with said second junction point through the normally closed contact of the second transfer element of the third relay, a fifth subcircuit connecting said second junction point with a third junction point through the normally open contact of the second transfer element of the third relay, a first output circuit connecting said third junction point with a first output locality through the normally open contact of the second transfer element of the first relay, a second, output circuit connecting said third junction point with a second output locality through the normally closed con tact of the second transfer element of the first relay, a sixth subcircuit connecting a point intermediate the normally closed contact of the first transfer element of the fourth relay and the normally closed contact of the first transfer element of the fifth relay to a fourth junction point through the normally open contact of the first transfer element of the fifth relay and the normally closed contact of the third transfer element of the third relay, a third output circuit connecting said fourth junction point to a third output locality through the normally closed contact of the third transfer element of the second relay, a fourth output circuit connecting said fourth junction point to a fourth output locality through the normally open contact of the third transfer element of the third relay, a seventh subcircuit connecting a point inter mediate the normally closed contact of the first transfer element of the first relay and the normally closed contact of the first transfer element of the fifth relay in the third subcircuit with a fifth junction point through the normally open contact of the first transfer element of the fourth relay, a fifth output circuit means connecting said fifth junction point to a fifth output locality through the normally open contact of the third transfer element of the first relay, a sixth output circuit connecting said fifth junction point to a sixth output locality through the normally closed contact of the third transfer element of the first relay, an eighth subcircuit connecting a point intermediate the normally closed contact of the first transfer assembly of the first relay and the normally open contact of the second transfer element of the second relay in the first subcircuit to a sixth junction point through the normally closed contact of the second transfer element of the second relay, a ninth subcircuit connecting said sixth junction point to a seventh junction point through the normally open contact of the first transfer element of the third relay and the normally open contact of the second transfer element of the fifth relay, a tenth subcircuit connecting said sixth junction point with a seventh junction point through the normally open contact of the second transfer element of the fourth relay, a seventh output circuit connecting said seventh junction point to a seventh output locality through the normally closed contact of the second transfer element of the fourth relay, an eleventh subcircuit connecting a point intermediate the normally open contact on the first transfer element of the third relay and the normally open contact on the second transfer element of the fifth relay in the ninth subcircuit with an eighth junction point through the normally closed contact of the second transfer element on the fifth relay, a twelfth subcircuit connecting a point intermediate the normally open contact of the first transfer element of the first relay and the normally closed contact of the first transfer element of the second relay in the second subcircuit to said eighth junction point through the normally open contact of the first transfer element of the second relay and the normally closed contact of the third transfer element of the fourth relay, an eighth output circuit means connecting said eighth junction point to an eighth output locality through the normally open contact of the third transfer element of the fourth relay, a thirteenth subcircuit connecting a point intermediate the normally open contact of the first transfer element of the third relay and the normally open contact of the second transfer element of the fifth relay in the ninth subcircuit to a ninth junction point through the normally closed contact of the first transfer element of the third relay, a ninth output circuit connecting said ninth junction point with a ninth output locality through the normally open contact of the third transfer element of the fifth relay, and a tenth output circuit connecting said ninth junction point to a tenth output locality through the normally closed contact of the third transfer element of the fifth relay.

4. The relay network as set forth in claim 3 wherein each of said relays has a fourth transfer element available for holding purposes.

5. A distribution network for selectively providing three electrical paths from a common input locality to three output localities comprising first, second and third switching devices, each of said switching devices including pairs of terminals and means for selectively estab lishing alternate conductive paths between at least two of said pairs of terminals in response to alternate ones of two conditions of operation of said switching devices, said pairs of terminals being arranged in electrical circuit with conducting means to provide a first subcircuit connecting the input locality to a first junction point through the first pair of terminals of the first switching device, a second subcircuit connecting the input locality to a second junction point through the first pair of terminals of the second switching device, a third subcircuit connecting the first and second junction points through the first pair of terminals of the third switching device, a first output circuit including a second pair of terminals of the first switching device connecting the first junction point to a first output locality, a second output circuit including a second pair of terminals of the second switching device connecting the second junction point to the second output locality, and a third output circuit includ ing a'second pair of terminals of the third switching device connecting the second junction point to the third output locality.

6. A distribution network for selectively providing three electrical paths from a common input locality to three output localities comprising first, second and third switching devices, each of said switching devices including pairs of terminals and means for selectively establishing alternate conductive paths between at least two of said pairs of terminals in response to alternate ones of two conditions of operation of said switching devices, said pairs of terminals being arranged in electrical circuit with conducting means to provide a first subcircuit connecting the input locality to a first junction point through the first pair of terminals of the first switching device, a second subcircuit connecting the input locality to a second junction point through the first pair'of terminals of the second switching device, a third subcircuit connecting the first and second junction points through the first pair of terminals of the third switching device, a fourth subcircuit connecting the second junction point to a third junction point through the second pair of terminals of the first switching device, a first output circuit connecting the first junction point to a first output locality through a pair of terminals of the first switching device, a second output circuit connecting the third junction point to the second output locality serially through the second pair of terminals of the third switching device and the second pair of terminals of the second switching device, and a third output circuit connecting the third junction point to the third output locality through a pair of terminals of the thirdswitching device.

7. A distribution network for selectively providing three electrical paths from a common input locality to three output localities comprising first, second and third switching devices, each of said switching devices including pairs of terminals and means for selectively establishing aiternate conductive paths between at least two of said pairs of terminals in response to alternate ones of two conditions of operation of said switching devices, said pairs of terminals being arranged in electrical circuit with conducting means to provide a first subcircuit connecting the input locality to a first junction point through the first pair of terminals of the first switching device, a second subcircuit connecting the input locality to a second junction point through the first pair of terminals of the second switching device, a third subcircuit connecting the first and second junction points through the first pair of terminals of the third switching device, a first output circuit connecting the first junction point to a first output locality through the second pair of terminals of the first switching device, a second output circuit connecting the second junction point to the second output locality through the second pair of terminals of the second-switching device, and a third output circuit connecting the second junction point to the third output locality serially through the second pair of terminals of the third switching device and a pair of terminals of the first switching device.

8. A relay distribution network for selectively providing three electrical paths from a common input locality to three output localities comprising first, second and third relays, each of said relays having first and second fixed contacts and a transfer contact shiftable from engagement from one to the other in response to one of two conditions of operation of said relays and one of said relays having a third fixed contact and a second transfer contact shiftable in and out of contact therewith, said contacts arranged in electrical circuit with conducting means to provide a first subcircuit connecting the input locality to a first junction point through the first contact of the first relay, a secondrsubcircuit connecting the input locality to a second junction point through the first contact of the second relay, a third subcircuit connecting said first and second junction points 7 through the first contact of the third relay, a first output circuit connecting the first junction point to a first output locality through the second contact of the first relay, a second output circuit connecting the second junction point to the second output locality through the second contact of the second relay and the third contact of the first relay, and a third output circuit connecting the second junction point to the third output locality through the second contact of the third relay;

9. A relay distribution network for selectively providing three discrete electrical paths from a common input locality to three output localities comprising first, second and third relays, each of said relays including at least a normally open contact, a normally closed contact and a transfer contact displaceable from engagement with the normally closed contact into engagement with the normally open contact in response to actuation of the relay associated therewith, said contacts arranged in electrical circuit with conducting means to provide a first subcircuit connecting the input locality to a first junction point through the first normally open contact of the first relay, a second subcircuit connecting the input locality to a second junction point through the normally open contact of the second relay, a'third subcircuit connecting said first and second junction points through the normally open contact of the third relay, a first output circuit connecting the first junction point to a first output locality through the normally closed contact of the first relay, a second output circuit connecting the second junction point to a second output locality through the normally closed contact or" the second relay and the second normally open contact of the first relay, and a third output circuit connecting the second junction point to a third output locality through the normally closed contact of the third relay.

10. A relay distribution network for selectively providing three discrete electrical paths from a common input locality to three output localities comprising first, second and third relays, each of said relays including at least a normally open contact, a normally closed contact and a transfer'contact displaceable from engagement with the normally closed contact into engagement with the normally open contact in response to actuation of the relay associated therewith, said contacts arranged in electrical circuit with conducting means to provide a first subcircuit connecting the input locality to a first junction point through the first normally closed contact of the first relay, a second subcircuit connecting the input locality to a second junction point through the normally closed contact of the second relay, :1 third subcircuit connecting said first and second junction points through the normally closed contact of the third relay, a first output circuit connecting the first junction point to a first output locality through the normally open contact of the first relay, a second output circuit connecting the second junction point to a second output locality through the normally open contact of the second relay and the second normally closed contact of the first relay, and a third output circuit connecting the second junction point to a third output locality through the normally open contact of the third relay.

References Cited in the file of this patent Publication, Some Basic Relay Circuits, by Keister et al., Bell Telephone System, copyright 1948.

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