Patent GB-229761-A (GB)
Title: Improvements in or relating to semi-automatic telephone systems
IPC: H04M3/60
Filed: 1923-11-29
Abstract: 229,761. Automatic Telephone Manufacturing Co., Ltd., and Ostline, J. E. Nov. 29, 1923. Semi-automatic exchange systems.-In a system in which calls from a manual exchange are set up through a semi-automatic tandem exchange, the wanted number is passed from the A-operator over an order wire to a B-operator who assigns an idle trunk and sets up the number on her keyset. The B-operator has no other duties either of an operating or of a supervisory nature, and is protected from interruption by the application of a mild tone to all the order wires. Special operations to rectify errors are performed by the operator who makes the error. A warning signal is given to the A-operator if she plugs into an unassigned trunk, and if an assigned trunk for any reason is not taken up by the A-operator within a given time, it is automatically released. The tandem exchange is similar to that described in Specification 229,765 in which a plurality of impulse senders are available in common to several operators over switches, and in order to increase the speed of operation, the wanted number is first registered in relay sets individual to the position and is subsequently transferred to relay sets associated with the selected impulse sender. General operation. The B-operator receives the wanted number over the order wire 1, 2 and assigns a trunk 10, 11 by pressing the assignment key 12, energizing relay 13 which locks, removes earth from the test terminal 60 of the trunk finder, and grounds wire 70. Relay 77 energizes, locks and connects mild tone from a source 80 to wire 6 to indicate to the A-operators that the B-operator is engaged. A circuit is also closed over wiper 75 for the line relay 150, which connects up the stepping magnet 153 and switching relay 154 of the trunk finder, which hunts in the usual manner. Relay 163 energizes in parallel with relay 150 and connects up the stepping magnet 167 and switching relay 169 of the sender selector, which hunts for an idle impulse sender. Meanwhile the B-operator sets up the wanted number on her keyset. In response to the first digit, earth is connected to one or more of the wipers 71-74 of the outlet finder to energize one or more of the storage relays 95-97, which lock and mark contacts in the banks of a transfer switch 191-196. Relay 85 energizes in series with the storage relays, and two-step relay 87 partially operates over its lower winding and connects up at contact 88 its upper winding, which is short-circuited until relay 85 falls back on the release of the digit key, whereupon relay 87 operates fully and connects up the second set of storage relays and the second twostep relay 110. Further contacts of the transfer switch 191-196 are marked in response to the remaining digits in a similar way. Switching relays 154, 169 upon energizing connect earth at contact 174 to the test wipers 160, 168. Relay 18 therefore operates over its upper winding, locks, grounds the test wire 31 leading to the first selector and connects up its lower winding over contacts of a dash-pot relay 29, which is also connected up but is short-circuited at test contact 60. The outgoing trunk 32, 33 is connected to contacts 61, 62 and relay 13 is released. Assuming that the A-operator plugs in before the B-operator has set up the complete number, battery on wire 11 energizes relay 34 which open-circuits the lower winding of relay 18, connects up the polarizing winding of relay 47 and operates relay 41, which locks, lights lamp 52, and places a further earth on wire 31. The B-operator presses the start key 81, and relay 82 energizes, releasing relay 77 to remove tone from the order wires and connecting up the stepping magnet 68 of the outlet finder. The magnet 184 of the transfer switch 191-196 is also connected up over wires 185, 186 and interrupter springs 188, relay 176 being energized at this time, and the digits are thereby transferred over the sender selector to sets of storage relays associated with the impulse sender, which then operates as in Specification 229,765. Relay 212 energizes over the tenth contact of wiper 196, locks and operates relay 197, which connects wipers 161, 162 to the impulse wires 206, 208, releases relay 169 and grounds wire 203 to initiate impulse sending. Earth is removed from wire 209 when this is completed, and relays 212, 197 relapse, so that relay 154 falls back and releases switching relay 18, which is not held by the current in its upper winding. The called subscriber is rung, and upon his replv the reversal of current operates relay 47, which connects up a choke coil 51, operating the supervisory relay at the A-operator's position. and giving her answering supervision. Busy signal. Earth and battery are applied alternately to wire 33, intermittently releasing relay 48 by short-circuiting and energizing busy relay 56, which connects battery to wire 10. The supervisory lamp at the A-operator's position is thus caused to flash. Trunking arrangements. If the assigned trunk is not taken up by the A-operator, relay 34 does not energize and after impulse sending, relay 18 remains energized over its lower winding. Dashpot relay 29 is no longer short-circuited and opencircuits relay 18 after a given time, and the connection is released. If the A-operator plugs into an unassigned trunk, relay 34 energizes and connects an interrupter 53 to wire 11 to flash the supervisory lamp, preferably at a rate different from that of the busy signal. Special keys and lamps. The cancellation key 115 controls relay 202 which upon operation removes earth from wire 90, releasing the storage relays. The disconnect key 211 marks the outlet busy and lights lamp 219. Relay 210 operates when all the senders are busy or when a fault occurs in the trunk finder and has a similar effect. The trunk lamp 52 lights when the trunk finder comes to rest or when the A-operator plugs in.