Patent GB-266063-A (GB)
Title: Improvements in or relating to telephone exchange systems
IPC: H04Q3/00
Filed: 1925-11-20
Abstract: 266,063. Standard Telephones & Cables, Ltd., (Bell Telephone Laboratories, Inc.). Nov. 20, 1925. Automatic exchange systems.-In a system in which the dialled number is received by an impulse recorder which transfers it to a marker, a number of equivalent markers are provided which are common to the recorders and the arrangements are such that several connections can be marked out simultaneously. The recorders engage the markers in different orders of preference. The markers are divided into two groups which have access to the selector circuits by multi-contact relays through two channels, one group of markers using by preference one channel and the other group the other. If a marker meets trouble it releases itself and the same or another marker is taken into use, and this marker, whether or not it belongs to the same group, uses the channel that was not used by the first. The markers are provided with chains of test relays for finding idle trunks and links of desired numerical groups, and these chains are designed to deal with groups of different sizes, only part of a chain being employed when testing a group of less than full size. General operation. The circuits illustrated deal only with. the extension of a call through a cross-bar group selector 105 of the link-circuit type in accordance with the first three dialled digits, which result in the energization of a marker code relay 402 individual to the wanted exchange. A trunk 102 seized by a calling subscriber is connected by switch 111 to a recorder, scme elements of which are shown at the left of Fig. 1, and this is connected to a marker such as that shown in Fig. 3 and at the left of Fig. 4 by multi-contact relays 203,205. The recorders are divided into two groups having access to the markers over separate channels 201, 202. Each recorder has access to every marker, but only one connection at a time can be made over each channel. The markers have access by multicontact relays over channels 500, 501 to the operating magnets of the selector 105 and to the test circuits of the links such as 126, and over channels 600, 601 to the test circuits of the trunks outgoing from the selector. The marker shown in detail, employs by preference, the channels 501 and 600, but the energization of a relay 411 transfers its operations to the other channels. On the other hand the marker 440, shown in blank at the right of Fig. 4, belongs to the other group and employs by preference the channels 500 and 601. Seizure of marker and transfer of record thereto. At a suitable stage in the operation of the recorder, relay 114 is energized to close the circuit 128 of relay 211, which locks itself in series with relay 212 to prevent the seizure of the channel 202 by any other recorder. Relay 203 is energized and, provided the marker shown in Fig. 3 is idle energizes relay 209. (If this marker had been busy the circuit of relay 209 would have been opened by a busy relay 207, and the relay such as 218 of another marker would have been energized). Relay 209 locks itself in series with relay 210, which energizes relays 205, 208 and the busy relays 207, 213. (It should be noted that the recorders connected by relays 203, 204 engage by preference the marker connected by relay 205, while the recorders connected by relays 215, 216 engage by preference the marker connected by relay 206). The recorder is now connected to the marker and transfers the record of the first three digits to the relay registers 300, 301, 302. Assuming that relays 305, 306, 350, 307, 351 are energized it will be seen that relays 304, 313, 314 are energized and that a circuit 316 is picked out to energize the code relay 402. Control of the selector 105. Relay 400, which is energized as soon as the marker is seized, closes circuits through back contacts of relay 411 for relays 506, 605 which energize relays 510, 604 to connect the marker to the channels 501, 600. The code relay 402 energizes a relay 602 individual to the wanted group of trunks 123 to connect the test circuits 612 of these trunks to the channel 600 and thence over circuits 420 to the right-hand windings of the test relays of the chain 409. It is assumed that there are four selectors such as 105 in the exchange, and that these are connectable to the channel 501 by relays 508, 509, &c. It is necessary in the present instance to energize the relay 508 individual to the selector shown. This is accomplished by a circuit 417 which has been prepared by the energization of a relay 403 belonging to a group of relavs 403 - - 406, two sensitive and two marginal, controlled over a circuit 119 to which either ground or battery, direct or through a resistance. is applied from the selector. If the call had come through another selector, another of the relays 403 - - 406 would have been energized and would have closed a circuit for another of the relays 508, 509, &c. Circuits 513, 121 and 514, 122 are now closed from the code relay 402 through the channel 501 to energize the vertical marking magnets 106, 107 corresponding respectively to the trunk 102 and to the wanted group of outgoing trunks 123, and a test is made in the marker to find an idle trunk of which the corresponding link circuit in the selector 105 is also idle. It has been pointed out that the right-hand windings of the test relays of the chain 409 are connected to the trunk test circuits. The lefthand windings are connected through the channel 501 over circuits such as 424. 516 and right-hand windings of magnets 108 to the test circuits of the corresponding links, so that a test relay is energized if either a trunk or the link giving access to it is busy, and when a slow-to-energize relay 408 pulls up it closes a circuit for a relay such as 422 corresponding to the first available link 126 and trunk 124. Relay 422 grounds the circuit 424, 516 to energize the link operating magnet 108 which completes the connection. In the present instance it is supposed that the group of trunks 123 is not of the full size, and the code relay 402 accordingly picks out a relay 408 which investigates the test chain 409 at an intermediate point in its length, the relays below 421, 422 not being brought into play. Operations when a marker meets trouble. If a marker of the first group fails to complete its functions and release itself within a predetermined time, a timing device 401 releases it and closes a circuit 426, 220 to energize relay 116, which locks itself in series with relay 115, which closes circuit 128 to cause a fresh seizure of a marker. Circuit 129 is now grounded through a resistance, so that if the marker now seized is of the same group as before, sensitive relay 410 but not marginal relay 412 is energized and a circuit is completed for relay 411, which results in channels 500, 601 being used instead of channels 501, 600. On the other hand, if the marker now seized is of the other group, for example 440, which gives preference to the channels 500, 601, these channels are used since relay 416 is marginal and does not respond. Again, if a marker of the second group such as 440 meets trouble, it closes circuit 450 to energize relay 117 instead of 116 and the circuit 129 is directly grounded, so that if the second-trial marker is of the first group, both relays 410, 412 are energized and 411 is not energized, but if the second-trial marker is of the second group, relay 416 responds and energizes relay 441. Thus in all cases a second trial.is made over different channels from the first.