Patent GB-476587-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04M3/28
Filed: 1936-06-11
Abstract: 476,587. Automatic exchange systems. ASSOCIATED ELECTRIC LABORATORIES, Inc. June 11, 1936, No. 16345. Convention date, July 12, 1935. [Class 40 (iv)] A two-motion test distributer at a centralized test position acts as a two-digit switch on one level for connections to local lines and as a single-digit group selector on other levels for connections to lines in other exchanges. The system described employs five-digit numbers of which the first denotes the exchange. In the local exchange, the third digit sets a single-motion test-connectorselector whilst in other exchanges the second and third digits set a test distributer which may be similar to that shown. Six-conductor trunks connect the switches in the local exchange and four-conductor junctions extend between the exchanges, the test distributer being arranged to repeat loop selecting-impulses in both cases, but to repeat other control signals, such as battery or ground on one leg, either modified or unmodified according to the destination. Testing lines in the same exchange. Relays 8, 10, 11 operate and impulses of the first two digits control the magnets 20, 21 in known manner and in the interval between the relapse of relays 16, 17 a busy-test is made over wiper 24. If the connector-selector is busy, relay 15 operates in series with 17 energizing relay 7 which reverses the connections to conductors 3, 4 to give a signal to the clerk. If idle, relay 18 operates and extends a loop over wipers 25, 26 over which the third digit is repeated by relay 10. If the test connector selected is busy,. battery on lead 81 will operate relays 15, 7 to give a busy signal as before. If idle, the last two digits are repeated over wipers 25, 26 to set the test connector and the called line is tested as regards its busy condition by the connection of relay 7 to wiper 23. If idle, ground 32 applied to this wiper on the relapse of relay 17 operates the cut-off relay. To release the cut-off relay for making an inward test, key BCO is thrown, holding relay 10 but releasing relay 8. The throwing of key CR releases 10 and holds 8 whereby the connectorselector and connector are released and may be reset to another line. Testing lines in another exchange. If the first digit dialled corresponds to another exchange, springs S are operated to close a locking circuit for relay 19 which is energized during the vertical movement. On the relapse of relay 12 relay 16 operates over resistance 76, but the rotary magnet does not yet operate. Relay 16 completes a circuit for relay 13 which switches over from two-digit to single-digit working completing at 48 a direct circuit for magnet 21 which then interacts with relay 19 to hunt for an idle test distributer in the other exchange. For all lines except the last in the group, contacts of wipers 23, 24 are strapped together so that relay 19 connected to wiper 23 operates over ground placed on wiper 24 in busy circuits. If the last line is also busy, relay 19 does not operate but relay 15 operates over wiper 24 and gives the busy signal. When an idle line is found, relay 18 operates on the relapse of 16 extending a loop to wipers 25, 26 over which further impulses are repeated to the distributer at the other exchange. If a busy condition is encountered, polarized relay 14 operates to energize relay 7 and to extend a path for the busy tone back to lead 4. Relay 9 operated when either relay 8 or 10 falls back repeats over wipers 25, 26 circuit changes corresponding to those produced in leads 3, 4 when keys BCO, CR are operated. Specification 291,510, [Class 40 (iv)], is referred to.