Patent GB-269236-A (GB)
Title: Improvements in automatic and semi-automatic telephone systems
IPC: H04Q3/42
Filed: 1926-01-07
Abstract: 269,236. Standard Telephones & Cables, Ltd., (Deakin, G.). Jan. 7, 1926. Automatic exchange systems. - In a system employing link circuits comprising backwardhunting and forward-hunting switches the controlling equipment for the link circuits other than the stepping magnets and a switching relay is located in the register-controller which controls the setting up of a connection, and is associated with a link circuit over a non-numerical switch. An exchange having 900 lines is described employing 300 point connectors of the trip-spindle type, the selection of a connection of the desired group being controlled by means of a multiple connection from the test wire of each connector to the correct terminal of the first digit register in the register-controllers. The first digit subsequently controls the advance of the connector wipers to the section of the bank in which the wanted line lies before the units digit is effective. Some of the connectors D may be modified for dealing with calls to a private branch exchange. Connection of register-controller to calling line and registration of the wanted number. Line relay LR energizes relays FSR, ASR to connect up the magnets PS of the idle register-controllers, and to connect battery potential to terminal j of all the idle link circuits having access to the calling line. On an idle link circuit being reached, test relav RTIR energizes, and connects up relay RT2R, which connects in the low resistance winding of relay RT1R. Magnet PF is now connected up over terminal k to cause the switch LF to hunt for the calling line. When this is found, test relay RT3R energizes over terminals d, l, and connects up relay RT4R, which connects in the low resistance winding of relay RT3R. Relay FSR is short-circuited, and falls back, releasing relay ASR. If the latter relay remains energized for an excessive time. a timing-device TA1 lights lamp LGL. Relays RAR, RBR, energize placing busy ground on terminal j and over terminals m, c connecting up relays RHR, COR, the former of which locks relays RAR, RBR. Impulse relay 1SR is now connected to the calling line and energizes. advancing the sequence switch R to position 3, in which dialling tone DTC is connected up, and release relay LBR operates. The first digit is repeated by relay 1SR to the magnet of the first digit register DS1, with slow-to-release relay LMR in parallel. This relay on energization moves the sequence switch to position 4, and on relapsing at the end of the impulse train moves it to position 5 to connect up the second digit register DS2. The second and third digits are stored in the registers DS2, DS3, and lamps PL1, PL2, PL3 are controlled to indicate progress. Relay 1AR is a quickacting relay which ensures full energization of the register magnet. Selection and control of connector. In position 8 of the sequence switch, there is an energizing circuit for the high-resistance winding of relay RT1R through a common resistance, and this relay energizes provided no other register-controller is standing in position 8. Relay RT2R pulls up, and magnet PJ operates over terminal t to rotate the switch JF in search of an idle connector in the desired group. Assuming the first digit is 6, test relay RT3 energizes over terminals s, i and a multiple connection to terminal 6 of wiper B1, and a connector serving the group of lines whose first digits are 4 - - 6 is chosen. Relay RT4R energizes and advances the sequence switch to position 9. If the register-controller remains in position 8 for an excessive time, a timing-device TA3 effects release by short-circuiting relay RHR. The fundamental circuit J, e, q, N, OSR, p, f, I, FLR is now closed, and relay FLR energizes and advances the connector sequence switch R to position 2, in which the trip spindle magnet P2 is connected up. Relay OSR energizes and advances the reverting switch RS which is controlling by an interrupting relay OBR to position 1, and at each step of the trip spindle a ground impulse is sent back from commutator COM2 to short-circuit relay OSR and advance the switch RS. When the correct number of impulses have been sent back, a circuit is closed over wipers D2, C4 for relay OAR, which opens the fundamental circuit and advances the sequence switch to position 10. The switch RS restores to normal, and the sequence switch moves into position 12. Relay FLR on relapse advances the connector sequence switch to position 3. The fundamental circuit is again closed, and the sequence switch advances to position 4, in which the wiper magnet PI operates, impulses being sent back from commutator COM1. The preliminary movement of the wipers is controlled by relays SHR, THR, which are connected up over wiper 01. If the first digit is 1, 4, or 7, neither is energized, if it is 2, 5 or 8, then relay SHB is energized, while if it is 3. 6 or 9, both are energized. In the present instance, both are energized and are held in position 12 over wiper B4 of the reverting switch RS, so that 20 impulses must be received before these relays are released and relay OAR is connected to wiper C4. The units selection then takes place in the usual manner. Relay OAR advances the sequence switch to position 1 and the registers and the reverting switch are restored to normal. Relay FLR falls back and advances the connector sequence switch. In positions 5 - - 7, switching relay LCR of the link circuit energizes over terminals h, r and locks, marking the link circuit busy and lighting lamp BL. Relay RHR is shortcircuited over terminals g, m and the registercontroller is released. Feed relay SIR energizes. Completion of connection and release. If the wanted line is free, test relay FTR energizes in position 5 and locks. Preliminary ringing current is connected up in position 10, and the usual intermittent ringing current from W1, GR is applied in position 12 to which the sequence switch is advanced by means, of interrupters W2, W3. Upon the reply of the called party, relay RGR energizes and drives the sequence switch to the talking position 16, booster battery being applied at cam K to the third wire to operate the meter SM. Feed relay S2R energizes. If the calling party hangs up first, relay SIR falls back and advances the sequence switch to position 17. Switching relay LCR releases, and lamp LCL lights until the called party hangs up. Similarly, if the called party hangs up first, lamp LCL lights in position 16 until the calling party hangs up. Relay S2R upon release advances the sequence switch to position 18 in which the magnets P1, P2 restore, and the sequence switch moves to position 1. Busy condition. If the wanted line is engaged, test relay FTR does not operate, and the sequence switch stops in position 8, in which busy tone BT1 is connected up. When the calling party hangs up, relay S1R falls back and advances the sequence switch to position 9 in which the magnets P1, P2 restore. The sequence switch is then advanced to position 1. If all the connectors in the wanted group are in use, in position 8 of the register-controller sequence switch, chain relay SMR energizes over wiper C1 or wipers C1, C2 in series with relay ABR, which disconnects relay RT1R to prevent interference with other register-controllers and connects up busy tone BT1 to the transformed DTC. A statistical meter TM4 is operated. Connector arranged for P.B.X. hunting. The dotted line connection between cam E and the back contact of test relay FTR is added. If the first line of the group is busy, the sequence switch stops in position, since relay FLR is energized. The magnet P1 therefore operates until an idle line is found, when test relay FTR pulls up and releases relay FLR. If all the lines of the P.B.X. group are busy, relav FTR pulls up over the last line, the cut-off relay COR of which is shunted by a resistance, but falls back when the sequence switch moves out of position 6, so that the sequence switch stops in position 8 and a busy signal is transmitted. Special service calls, e.g. 03. After registration of the second digit, the register-controller sequence switch moves to position 7, and then over wiper D1 to position 8. The switch JF hunts for a special service line, the test circuit passing over the appropriate terminals of wipers B2, B1. Relay RT4R advances the sequence switch to position 9, and thence it returns to normal. Calling line defective. The register-controller remains in position 3 if no impulses are received, and a timing-device TA2 operates and energizes relay TAR, which advances the registers DS1, DS2 to position 10, and the sequence switch to position 8. The line is therefore extended to a special service line corresponding to the number 00. A statistical meter TM1 is operated.