Patent GB-652629-A (GB)
Title: Improvements in automatic switching systems
IPC: H04Q3/42
Filed: 1947-12-23
Abstract: 652,629. Automatic exchange systems. STANDARD TELEPHONES & CABLES, Ltd. Dec. 23, 1947, No. 33973. Convention date, March 11, 1941. [Class 40 (iv)] A register-controller transmits information to a marker in the form of a sustained forward signal which is only removed by a signal reverted from the selector to the register-controller. The selector may be equipped with means for suppressing the reverted signal should the same forward signal be required for setting the succeeding selector. The registercontroller is associated with the first group selector, which latter also contains the feed bridge. Seizure and operation of register-controller and 1st group selector. On seizure impulse relay 1 and holding relay 2 operate, followed by 3 and 12, the latter connecting up the registercontroller. The holding relay 28 therein pulls up and switch R05 goes to position 1 to connect up dialling tone. The first three dialled digits are repeated by relays 1, 31 to digit switches RO2, RO3, RO4 over distributer switch RO5 which then homes and registers the last digit itself. If the initial digit is required for setting the selector S1 only and does not require to be transmitted to any succeeding selectors, the appropriate contact of bank RO24 of the first register switch RO2 is connected to point Y. When this switch is set, relay 5 operates to energize sequence switch RO1 which advances to position 3 where 44 operates over RO13 to stop the switch. Selector S1 then hunts for a free outlet in the group marked on its C terminals by the setting of RO25, which brings up test relay 7 to interrupt the drive circuit for S1. Relay 5 thereupon releases by differential action and 10 pulls up to busy the succeeding selector and switch through. Relay 52 operates over the A wire, bringing up 35 momentarily in the register-controller over the B wire to move RO1 to position 4 where the second digit is transmitted to the marker of the second group selector. If the digit is one which requires transmission forward after setting selector S1, the appropriate contacts of the digit switch bank RO24 are connected to point X, so that switch RO1 is stopped in position 1 wherein the selector S1 is set as above. RO then goes to position 2 where the first digit is transmitted to the second group selector. The registered digits are signalled to the selector markers over the A and B wires. The digits are characterized in pairs by the application to the B wire by digit-switch wipers RO23, RO33 ... of one of the following five conditions, strong or weak positive or negative potential, or alternating current. Even digits are further characterized by low resistance earth applied to the A wire from wipers RO22, RO32 . . . (via the upper winding of 3). These conditions are applied in even positions of the sequence switch R01, the switch being moved from an odd to an even position by the operation of 35 over the B wire when a marker is associated with the selector. In this position 22 (followed by 21) operates over the B wire and when the registered digit has fulfilled its purpose, i.e. all the necessary selectors have been set by it, the B wire is opened by the last selector set to release 22, 21 and step the sequence switch to the next odd position. When all the selectors are set and RO1 reaches position 9, relay 26 operates, releasing the associating relay 12 and also release relay 28 in the register controller. When the last selector switches through, battery is removed from the A leg to release 3 and complete the talking circuit. Ringing and called subscriber reply operations are effected in known manner. If the called subscriber is busy, battery reverted over the B leg operates 6 to short-circuit 2 which removes ground from the T wire to effect the sending of busy signal. Setting of group selector, Fig. 3. When the selector is seized associating relay 52 operates to high resistance battery over the A leg to connect up the marker. A combination of the marking relays 58, 59, 60, 64 appropriate to the registered digit respond to the conditions applied over the A and B wires to mark the C-terminals of the required group and 56 operates to start the selector. When the selector finds a free line of the group, whose marking circuit is also free, 55 operates, stops the selector and releases 56 by differential action. 57 pulls up, followed by relay 51 which switches through and releases the marker. If the digit is such that it is required to set S2 only, 57 in operating opens the B wire to signal to the register controller that a subsequent digit is to be sent. If, however, the same digit is required for setting the succeeding selector, 'relay 80 operates over the marking wire to retain the B wire circuit closed. Setting of connector. Associating relay 81 operates over the A wire on seizure followed by 91 and 87. If the tens digit is even, earth in the A wire operates 90 which brings up the wiper switching relay 83. An appropriate combination of 93, 94, 95 operates according to the condition on the B wire and the selector hunts for the marking so applied to the tens C-terminal. When this is found 84 operates to stop the switch and 92 follows to open the B wire circuit, causing the register controller to disconnect the digit characterizing conditions whereupon the marking circuit is disconnected and 84 releases. Relay 97 operates during the consequent slow release of 92 followed by 97<SP>1</SP>, which connects the hitherto unused marking relay 96 to the A wire. Release of 92 completes the B wire circuit and the register transmits the next digit, which is received by the marking relays 93 ... 96, whereupon RC1 hunts for the marked contact, the finding of which brings up 84, and 86 operates during the slow release of 92 to bring up 89. If the subscriber's line is idle, 88 operates over the TC wire, releasing 87 by differential action (its lower winding being energized over the T wiper) to bring up 90 and the relay 82 switches through during the subsequent slow release of 91 and releases the marker. If the called subscriber is busy 87 is not released, 90 does not operate and busy battery is reverted over the B wire and busy tone is reverted by the subscriber's line equipment as described in Specification 499,133.