Patent GB-706395-A (GB)
Title: Automatic switching system for telecommunications
Inventor: LESIGNE HENRI LOUIS
IPC: H04Q3/42
Filed: 1950-03-20
Abstract: 706,395. Automatic exchange systems. COMPAGNIE INDUSTRIELLE DES TELEPHONES. March 20, 1950, No. 6843/50. Class 40 (4) If all the outlets of a PBX group are busy a signal is sent to the register - controller to transfer the last three digits to switches in an auxiliary register-controller which thereafter controls the completion of the connection. The system is generally similar to that described in Specification 668,261, the selectors being controlled over common marking wires marked by individual batteries in the register-controllers. PBX groups of more than five lines are split between two groups of final selectors. The auxiliary register repeatedly tests small PBX groups but makes no attempt to complete a connection to a large PBX group until a line is freed. The terminals of the individual battery of the auxiliary registercontroller; Fig. 3, are indicated by a small circle accompanied by + or -. Call to a large PBX group which consists of sub-groups Z4, Z5, Fig. 2, connected to the final selectors SDV2,. SDV3 respectively, and having relays 01, 02 which operate when the lines of the associated sub-group are busy._ By marking wire 536 the register-controller Ei extends the call over the outgoing selector of link Ci and selector SM2 to selector SMC1, which is set to a final selector SDV2, 3 having access to a free line of the wanted group by a marking applied over wire 530 and back contacts of the busy relays O1, 02. Should all the PBX lines be busy, wire 530 is connected over front contacts of the busy relays O1, 02 to mark all final selectors giving access to the wanted PBX group. When, say, final selector SDV2 reaches the first line of the group marked over wire 514, a circuit is completed over wire 515 for relay 26 in the register-controller, Fig. 4, and since wire 516 is disconnected, the register-controller ends the test for an idle line. Relay MGX in the link circuit Ci follows 26 to earth the start wire MM of the auxiliary register-controller. Relays 1a, 5 operate and the switch X11 couples the auxiliary registercontroller to the link Ci whereupon the test relay 5 is energized over an opposed winding and so releases. Relay 2 locks up, sequence switch X4 moves to position 2, 1a falls back and circuit is completed over wire 515 and the selector chain for relays 10, 11 which are followed by 17. Relay 4 energizes the driving magnet of the hundreds digit switch XI which hunts for a marking applied over a wire 527 and the hundreds digit switch X14 in the register-controller and connected up by relay 27 which was operated over 533. When X1 is set, relay 6 disconnects the driving magnet and operates 8 which shunts down 4. Relays 6, 8 release and the sequence switch moves to position 3. In a similar manner in positions 3, 4 of the sequence switch, the tens and units digits are transferred to the digit switches X2, X3 in the auxiliary registercontroller. The sequence switch X4 moves to position 5. When a line becomes free O1 or 02 falls back to disconnect wire 515, whereupon relay 26 releases the register-controller and the selector train. In the auxiliary registercontroller relays 10, 17 relapse, sequence switch X4 moves to position 6 and relays 4, 5 pull up. As soon as the selector in the link circuit Ci and the selector SM2 are released, a circuit is completed over wire 532 for relay 6. Earth from the selector SM2 energizes the opposed winding of relay 5, which releases to operate 8 which short circuits the high resistance winding of relay 6, so busying the selector SM2 which switches through to selector SMC1. Relay 3 locks up. Relays 4, 8, 6 fall back, the sequence switch X4 moves to position 7 and relays 4, 5 and 1a are energized. Supposing one of the lines Z5 has become free, the selector SMC1 hunts for the marking applied over relay 6 the digit switches XI, X2, X3 and wires 514, 525 and, when a free final selector SDV3 is found, relay 6 completes a circuit over relay 25. and the upper winding of 5. Relay 25 busies SDV3 and 5 releases to bring up 8 which shunts the high resistance winding of 6 to cause 19 to switch the connection through to the final selector SDV3. Relays 4, 6, 8 fall back, the sequence switch steps to position 9, and relays 4, 5 re-operate. When the final selector SDV3 passes over an outlet connected to a wire 531, there being one such outlet for each sub-group, relay 14 operates momentarily to bring up 15, 16. When a free line is found, relay 5 releases and relay 8 operates, followed by 22 which switches the connection through to the called line. Relays 4, 6, 8 release moving the sequence switch X4 to position 10. The line wires at the link circuit Ci are switched through by 18 which releases 2 whereupon the digit switches X1 ... 3 are homed and 11  releases. The sequence switch X4 steps to position 1 and the auxiliary register is released. Should the final selector SDV3 fail to find the freed line, relay 14 operates for a second time when the outlet connected to wire 531 is reached. The sequence switch X4 steps on to position 5, breaks the driving circuit for the final selector SDV3 and shunts down 4. Relays 10, 17 re-operate. When another line is freed, another attempt is made in response to the release of relays 10, 17. Call to a small PBX group.-When the final selector SDV1 reaches the last line of the PBX group 21 ... 23 and this is found to be busy, a circuit is completed over wire S17 to cause relay 26 to operate. The auxiliary register-controller is taken into use and the operations are as described above excepting that since there is no wire corresponding to 515 the relays 10, 11 and 17 remain back. Thus, when the sequence switch X4 reaches position 6, relay 3 is energized over a back contact of 11, and X4 steps to position 8. Relays 4, 5 operate, and the final selector SDV1 drives on. When the tens digit marking of the PBX group is found, relay 6 operates and 5 releases to bring up 8. Relays 4, 6, 8 release, the sequence switch X4 proceeds to position 9 and 4, 5 re-operate. Supposing all the lines are still busy, relay 5 remains operated. When the first line is reached, relay 6 causes relay 17 to operate momentarily to bring up 12 which prepares a circuit for 10. When the last line is reached 10 operates, followed by 17. At ten second intervals earth is applied under the control of a cam Cm to step the sequence switch X4 to position 2. Relays 12, 10, 17 release in turn. Relays.4, 5 fall back. The sequence switch proceeds to position 8 and a further search is made as described above. The cycle of operations is repeated until a free line is found. Graded service.-The links Ci associated with auxiliary register-controllers are accessible to operators and certain subscribers only.