Patent GB-415225-A (GB)
Title: Improvements relating to automatic telephone systems
IPC: H04Q3/00
Filed: 1933-05-24
Abstract: 415,225. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., Caxton House, Tothill Street, and DIXON, R. G., 162, Westmount Road, Eltham Park, both in London. May 24, 1933, No. 15013. [Class 40 (iv).] 200-point overflow primary finders AF giving access over each of two sets of wipers to different 100-line divisions (W, X) of a group of calling lines are taken into use by secondary finders FF which determine the division in which a selected primary finder will hunt. For this purpose, the sets of wipers of the primary finders are separately connected to the banks of different sets of wipers of the secondary finders and the operative set of wipers of the latter is determined by a marking applied by a primary allotter PA1, which allots and controls regular primary finders RF and starts a secondary allotter SA1 when no regular finder serving the calling line is available. The primary allotters serve six groups of primary finders and under overflow conditions mark the group of primary overflow finders in which the allotted secondary finder is to hunt as well as selecting the operative set of wipers in accordance with the division in which the calling line lies. All the finders and allotters are high-speed single-motion switches of the motor-driven latch-controlled type described in Specification 388,173. Regular finder RF. A primary start relay set PSR, Fig. 3, comprises four pairs of start relays A, E &c., one pair for each of four primary allotters PA1-PA4, the two relays of a pair being separately associated with the start leads W, X, of the two divisions of a 200-line group. If a call occurs in the X division relay PW is operated to connect up the X wipers of the allotter, and for calls from the first three of the six groups of calling lines served by the allotter, relay PG is operated to connect up the Y wipers. When an allotter is idle, relay PJ is normally operated. It will be assumed that a call occurs in the W division of the first line group and that the first allotter PA1 is idle. Relays A, PG, PGA, PS, PB operate and a circuit is completed for latch magnet MUP of the allotter. The group of calling lines is marked in bank 15 and when an idle regular finder in this group is reached relay PC operates over wiper 13. Relay PD now completes a circuit for the latch-magnet MU of the allotted finder and when the calling line is reached, quick-acting relay PE operates over wipers 3, Wp. Relays PEA, PEB, PF also operate, PEB opening the testing circuit and PF connecting earth to wiper 9 to operate switching relay HW which places direct earth on wiper Wp to operate the cut-off relay K. Relay PB releases and causes the allotter to return to normal, the arrangement of the circuits being such that this will always happen even if another call is waiting. Auxiliary finder AF and secondary finder FF. If the allotter PA1 finds all regular finders in the calling group busy, it moves to the end of its bank where it is stopped on one of the last three terminals by a jumpering to bank 15 individual to the calling group. Relays PC, PCA, PD, PP operate and a start circuit is completed over wiper 1 for a start relay SO of a secondary start relay set SSR. (Relay ST, Fig. 5, is marginal and only operates when two primary allotters seize the same secondary start set to take into use a second secondary allotter). Relay SO operates SA, SS, of the first idle secondary allotter, and this circuit may or may not include a winding of a wiperswitching relay SG. Relays SN, SP, SQ, SQA, SZ operate in succession and the latch magnet MUS is energized. When an idle secondary finder FF is reached, relays ST, STA, SR operate completing a circuit for the latch magnet MUF of the selected finder. When an idle auxiliary primary finder AF having access to the group containing the calling line is reached, relay SK operates over wipers 11, 13, 15 of FF and 9 of PA1 in series with relay PM which releases the primary allotter. In the secondary allotter relay SKB completes a circuit over wiper 5 or 6 and wiper 9 of FF for the latch magnet MUA of the primary finder and when the calling line is reached, relay SF operates over wiper 7 or 8 of SA1, 5 of FF, and the W test wiper of AF. Relays SF, SFA, SFB, SM operate similarly to PE, PEA, PEB, PF of the primary allotter, so that the cut-off relay K is not energized until after the switching relay H has operated. Busy conditions ; statistical metering. If no primary allotter is available when a call signal appears on wire W or X a corresponding meter OMW or OMX is operated. If no secondary finder is available in a required group, relays SU, SUA operate in the normal position of the allotter and when the end of the bank is reached, ST operates over resistance SLR. Relays SR, SL operate and complete a circuit over wiper 9 or 10 for a meter FFO individual to the secondary start relay set in use. An earth pulse on lead EP short-circuits ST and causes the allotter to recommence hunting. If no auxiliary finder in a required group is available to a secondary finder, relays SV, SX operate when wiper 10, Fig. 2, reaches its last contacts a first and second time, respectively, and a meter AFO individual to the secondary start relay set is operated over lead afo. Faults. If a primary allotter does not complete its operations within a predetermined time, a thermostat PZ energizes relay PA which gives an alarm and releases PJ to hold the allotter out of service. If relays PA in all the primary allotters are thus operated, a chain relay CL operates to restore them all to service. In a secondary allotter, the relays SN, SP, SQ, SQA, SZ, operated on seizure, release slowly in succession, and if SF has not operated when SQA releases, SM operates to release SS, SJ, so that the call is transferred to another allotter. Specifications 381,995 and 400,733 also are referred to.