Patent GB-262505-A (GB)
Title: Telephone exchange systems
IPC: H04Q3/42
Filed: 1925-09-05
Abstract: 262,505. Western Electric Co., Ltd., (Bell Telephone Laboratories, Inc.). Sept. 5, 1925. Semi-automatic exchange systems.-In an undeveloped system in which only one of the two code digits dialled is necessary to route a call to the wanted manual office, the unnecessary digit is suppressed by the number indicator register set. Preliminary operations; preselection of idle register set. Subscriber A is connected over non-numerical switches PLS. SLS and a first office-selector S to a trunk 105, 106 with a repeater R at its outgoing end. At the incoming end, line and release relays 101, 102 and relays 103, 104, 301, 302 pull up. Relay 103 and subsequently relay 302 ground the wire 130 to mark the register set busy. If any other switches such as 150 associated with idle trunks are standing on the terminals of the set, this ground energizes their relays 127 to cause their stenping- magnets 118 to drive them to the next idle set. Absorption of 2nd code digit and registration of subscriber digits. Relay 101 repeats the 2nd code digit over 137, 214, 114 to the sluggish relay 312 which energizes relay 313 which locks up. At the end of the digit, relay 309 which has hitherto been shunted out by 316 locks itself up and connects the impulse wire 304 to the stepping magnet 406 of the back-stroke thousands register TH which is operated by the next digit in series with relay 312. At the end of this digit, relay 308 is allowed, by the removal of shortcircuit 316. 371, 322, to pull up over 319, 371, 322 and switches over to magnet 416 of the hundreds register H. In a similar manner relays 307, 306 direct the remaining digits to the tens and units registers. Correcting duration of impulses. Relay 321, which is branched from the impulse wire, at each impulse locks itself over an interrupter contact on the stepping magnet to a front contact of the relay 301, thus maintaining the upper end of the magnet grounded until the completion of the stroke if the impulse relay fails to do so. Display of wanted number. At the end of the units digit, relay 312 completes a circuit over 435, 427 for relays 305, 303 which open the impulse circuit. Relay 305 unlocks the sequence relays, and relay 303 lights the trunk assignment lamp 201 over 133, 138. The operator then throws key 216 to energize relay 203 which locks up itself and relay 103, energizes relays 122, 128 which lock up, energizes relay 323 to cause the number to be displayed by grounding the arcs 401, 411, 421, 431, and flashes lamp 201. Relay 128 removes a shunt from the repeater coils and relay 122 disconnects relay 127. Completion of connection and release of register set. When the operator plugs in, relay 209 energizes relay 207 to complete the ringing circuit, and when the called party answers relay 208 allows relay 206 to shunt out relay 207 which completes the called loop to the battery feed. Relay 136 then energizes relay 107 to reverse the battery feed to the calling side for metering &c. Relay 209 also unlocks relay 203 which releases relay 323 to extinguish the indicator and relays 103, 104, 301 to initiate release of the register set. Relay 346 pulls up on the relapse of relay 301 and completes homing circuits for the registers, and when these reach normal is released by relay 302 which takes the busy mark off the wire 130. Release. When the calling party hangs up, relays 101, 102, 128, 122, 206 fall back and the disconnect lamp 210 which has hitherto been shunted out by relay 206 lights up. When the plug is withdrawn relay 209 releases the relay 136. Statistical metering. The key 216 operates a pe@ count meter. Displaying number at adjacent positions. If the key 202 is pressed instead of key 216, relay 205 energizes relay 211 which locks up in series with relay 345 which causes the number to be displayed at (say) the right-hand adjacent position. Relay 344 is controlled in a similar manner over 135 when the call comes in on a trunk of the other half-group to cause the display at the left-hand position.