Patent GB-761111-A (GB)
Title: Improvements in or relating to telephone systems
Inventor: PEARCE JAMES GORDON
IPC: H04Q3/00
Filed: 1953-08-07
Abstract: 761,111. Automatic exchange systems. AUTOMATIC TELEPHONE & ELECTRIC CO., Ltd. July 14, 1954 [Aug. 7, 1953], No. 20526/54. Divided out of 761,068. Class 40 (4). Subscribers can set up long distance connections automatically by connecting to an appropriate level relay set to take into use a register over a high-speed register connector which establishes an impulsing path between the subscriber and the register before the subscriber can dial the next digit. The register connector first attempts to connect to a register in a group of registers individual to the calling group of level relay rests. If all such registers are busy the register connector then attempts to seize a register in a group of registers common to several groups of level relay sets. The embodiment described uses cold cathode triodes and is described with reference to the schematic Fig. 1, the several selectors shown being multi-stage electronic devices. Seizing individual register. When the subscriber connects to a level relay set such as 1LRS1, it signals a start circuit (not shown) and a register hunt start circuit 1RHS, both common to all the level relay sets in the group 1LRS1-1LRS50. The start circuit marks the calling level relay set in hunt circuit 1LRSH. Similarly, 1RHS causes all idle registers in the individual group to maik corresponding positions in the individual register hunt circuit 1RHI, 1RHS then pulses the individual register hunt circuit 1RHI which seizes the first idle individual register, say 1REG1. This register biases the associated column of tubes in a coordinate array in the register connector 1RC. The register also pulses the level relay start hunt circuit 1LRSS. 1LRSS repeats the pulses after a slight delay to 1LRSH which is marked by the calling level relay set and pulses the corresponding row of tubes in the register connector 1RC. One tube CNT, Fig. 3, in the register connector therefore fires to produce an impulsing path between the calling level relay set and the selected register. This tube also operates a relay CN, Fig. 3, to establish a switching connection. Seizing common register. If all the individual registers are busy, the individual register hunt 1RHI signals over its final stage to a group start circuit IGS which marks the calling group in the group hunt circuit GH common to all the groups of level relay sets. 1GS also signals the group hunt start circuit GHS which repeats the signal after a delay to the group hunt circuit GH to find the calling group of level relay sets. The group hunt circuit GH then signals the common register hunt circuit 1CRH associated with the calling group of level relay sets to take into use the first available common register such as CREG1, after which 1CRH signals 1LRSS to operate 1LRSH as previously described. Impulsing path. When a register has been seized in the interdigital pause as described above, the first impulse of the next digit releases the A relay (not shown) in the level relay set. This operates relay IP (Fig. 2, not shown) which causes all tubes XF, Fig. 3, in the register connector to be pulsed, only that tube associated with the seized register striking to repeat the pulse to XFA, which pulses the register over lead IMP. When A (not shown) re-operates, IP (not shown) releases so that XF, XFA extinguish to terminate the impulse. Congestion in register connectors. If more than one subscriber connected to a group of level relay sets is waiting for connection to a common register, the first subscriber is connected in the manner described, relay CCO (Fig. 5, not shown) operating and then releasing to re-operate the group start circuit 1GS. The two cycles of the apparatus take longer than the normal interdigital pause so that if the second subscriber dials the next digit before the second cycle is completed busy tone is returned.