Patent GB-322190-A (GB)
Title: Improvements in or relating to call finders for automatic and semi-automatic telephone systems
IPC: H04Q3/00
Filed: 1928-08-29
Abstract: 322,190. Standard Telephones & Cables, Ltd., Wright, E. P. G., Baker, J. H. E., and Cameron, A. H. Aug. 29, 1928. Automatic exchange systems.-In a bi-direetional call finder system, the pilot switch is arranged to search for a second calling line if the line from which it commenced hunting is cleared or extended by another finder. If the switch is hunting vertically and the new calling line is on a level not yet reached the vertical stepping continues, whilst if rotary motion is taking place the switching continues to make the rotary search extending the new line if it is on the level being wiped over and has not been passed. Normal operation. Line relay L pulls up con. necting battery from KK to its private bank contact and operating relay LQS of the allotting switches. One relay such as LQS, LOS, LIS is. provided on each switch for each level. Relay LQS marks the required level on bank 3 of the pilot switch PS, connects at 2 earth to all contacts up to the level required on bank 1 of PS, at 4 connects earth to the finder bank contact of every disengaged line over contacts 3 of their line and cut-off relays L and KK, and at 3 completes a circuit for the common start relay CS. Relay CS operates followed by FR (wiper 1 of PS and CS6). G (SQ6 and CS6), E and F (via 2 and 2 of SQ and CS6), the last two locking up via contacts 1 and 2 of G and their own contacts 1. The finder FS is preselected by the switch AS and its vertical magnet V steps (wiper 4 of AS, CS7, DL2, SP3) in unison with magnet r of pilot switch PS, (DL1, CS5, SP1), the control being exerted by relay DL which is short-circuited by two paths respectively through rI and V1, which paths are broken as r and V pull up allowing DL to operate (CS6) to break the circuits of r and V to step the two switches. When the required level is reached relay SP operates (wiper 3 of PS and LQS1) energizing SQ (SP1) which locks SP to wiper 4 of PS and opens the short circuit of DL at SQ4 and 5. Relay SP breaks the vertical stepping circuit at 3 and completes a circuit for the lower winding of FR (SP2, Y3). The pilot switch is driven to its eleventh position by self interruption (r, SQ4, r1, wiper 2). Relay G remains operated (SQ6, G3, CS8, wiper 5 of AS, V1, R1) and magnet R operates (wiper 1 of AS, F2, E2, SQ3, CS6) stepping the switch and breaking the circuit of G releasing G, E and F and thus breaking its own circuit. G re-operates over contacts 3 of E and F and if neither of the lines on which the wipers are resting are calling (i.e. the wipers are earthed) E and F are re-energized (E over wiper 6 of FS, J3, wiper 3 of AS, E1, G1, and F over wiper 5 of FS, K3, wiper 2 of AS, F1, G2) and R reoperates. This cycle is repeated until either or both the wiper-sets rest on calling lines. If a calling line is engaged by wiper-set 2, 4, 6 a circuit is closed for relay J (wiper 6, J3, J, K4, SF1, E2, SQ3, OS6), the relay pulls up locking at contact 4 to the test wire and connects the calling line over its contacts 1, 2, 3 to the next switching stage. The test wire is grounded from SP3, Y, AS6. If the wiper-set 1, 3, 5 only finds a calling line, relay E energizes as before but relay F remains unoperated. Relay K pulls up (wiper 5 of FS, K, J5, SF2, F2, E2, SQ3, CS6) and the circuit is switched through. The circuit of K extending through an operated contact of E ensures that if both wiper sets engage calling lines, the set 2, 4, 6 is always connected. When the line is switched through relays KK and Y operatein series (SP3, Y, wiper 6 of AS). Relay KK locks up to the test wire at 3 and disconnects relay L. Relay LQS relapses and if two finders have been searching the unsuccessful one returns to normal. Relay Y locks up (Y3, SP2, FR) and CS releases (at Y1) driving switch PS from the 11th to the 12th position (SQ4) rI, CS4, wiper 2) and relay SP de-energizes followed by Y. When relay Y energized switch PS was in a position 2-11 and a circuit was closed for magnet d (Y2, PS4) to step AS one step. Relay then releases and d steps the switch AS (Y2, dI, NF of free finders in parallel, 12th contact of PS2) until a free finder is reached, when FR releases breaking the circuit. If all finders are busy the normal springs. NF of all finders are broken and consequently AS does not hunt until a finder is freed. When AS rests on a free finder, PS is driven to normal position over NF1. The first step of AS is independent of the returned earth over AS6 and consequently unless all other finders are busy the same finder is not used on two consecutive calls. When the calling party hangs up, relay J.or K releases and release magnet ZF is extended (J6, K6, NF2) to FR4 to release the finder if or as soon as FR is normal. Call abandoned. If during vertical movement the call is abandoned or extended bv another finder and no other caller is waiting, FR' releases, CS falls back and SP pulls up (CS1, PS4) and energizes SQ (SP1). Switch PS drives to position 12 (r, SQ4, rI, PS2) and if FS has then restored it is driven to its home position over NF1. The switch is released by ZF (J6, K6, NF2, FR4). In position 12 of PS, SP deenergizes and SQ falls back when PS reaches its normal position. If, however, another caller exists on the same or a higher level the switch continues to hunt until the calling level is reached. If the calling line is on a level that has been passed, relay FR relapses and the switch returns to normal as before. If the call is abandoned or extended by another finder on the rotary movement of the finder the switch continues to hunt. If another line is calling on the level in a more advanced position the circuit is extended as before described, otherwise the switch drives to the end of the bank operating 11th step springs SF, opening the circuits of K and J to prevent their operation and extending ZF at SF 3 to SF3 via Y to release the finder and operate Y to step AS to preselect another finder. PS is released as before.