Patent GB-664036-A (GB)
Title: Telephone exchange apparatus
IPC: H04Q3/00
Filed: 1949-11-17
Abstract: 664,036. Automatic exchange systems. WESTERN ELECTRIC CO., Inc. Nov. 17, 1949 [Nov. 17, 1948], No. 29429/49. Class 40 (iv).  In a register-sender used in a cross-bar tandem office for dealing with calls having either 3-digit or 2-digit office codes, the receipt of an initial digit denoting a 2-digit code causes the sequence control to skip the C register, so that the same registers are always used for the numerical digits. In the case of service codes which are prefixed with the digit 1 and are used to o btain connections to information and test boards &c. and TX codes which are prefixed with the digits 11 and are used in the completion of delayed toll calls and for other special purposes, the A register clears down in response to the prefix digit 1 (twice if necessary) and then takes the first digit following the prefix. Office codes. Digits are sent from an operator's keyset KS in a 2-out-of-5 frequency code and are received in a receiving circuit by channel relays which ground leads 0, 1, 2, 4 and 7 in pairs, as described in Specification 651,521. These leads are connected in turn to the relay registers by pairs of steering or " walking " relays AA, BB; BA, BB, &c., which are all energized upon seizure of the sender and are progressively released as the digits are registered. A start-pulsing signal is sent by relay RV1 when the sender is ready by reversal of the connections to the incoming trunk TR, and the wanted number is preceded by a signal which prepares the receiving circuit and is followed by a start signal indicating the end of pulsing. Excepi when the first digit is 1, as explained later, the operatec relays of the A register shunt out AB, and lock in series with TO which energizes, provided tw( register relays are in parallel anc releases the channel relays. In consequence, wire H is momen tarily ungrounded to release AA and direct the next digit to the B register. If more than two frequencies are received, relay OE operates over wire RO and con. trols RV1 to send a re-order signal. The operated relays of the A register ground the appropriate one of a set of terminals L2-L9, Fig. 8 (not shown), of which those corresponding to A digits allotted to 2-digit codes are jumpered to terminal TD. On the A digit of a 2-digit code, therefore, a circuit is made for relay TD which releases steering relays CA, CB, so that the C register is not used. Service codes and TX codes. A service code may be 100-109 or 120-199, and on the initial digit 1, the register relays do not lock and AB is not shunted out. Instead, a circuit is made over wire 609 for relay 11A, which connects up TO to clear down the channel relays and hence the A register, whereupon 11A<SP>1</SP> pulls up. The remaining digits of the service code are then registered on the A and B registers. On a TX code, which has initial digits 11, the second digit brings about the operation of 11B, 11B<SP>1</SP> the A register is cleared down twice, and circuit changes occur which allow the third digit to remain in the A register even when it is 1. Transfer of code to marker. On a 3-digit code, relay CL energizes when the C digit is registered and connects up DST which causes the seizure of a marker and the transfer of the A, B and C digits to the appropriate registers therein. On a 2-digit code, since TD is up, CL energizes when the B digit is registered. Moreover, TD effects circuit changes by which zero is recorded in the B register of the marker and the B digit is transferred to the C register. On service and TX codes, the start signal following the code digits grounds leads 7, 10 and thus brings up ST, DST to initiate the transfer. By the operation of 11A, 11A<SP>1</SP> the digit 1 is sent to the A register of the marker and the remaining digits of a service code go to the B and C registers. If the TX codes comprise two digits after the prefix, the connections marked S are used, and 1xx is sent to the marker as in the case of a service code. If, however, the TX codes comprise three digits, the connections marked T are used and those three digits alone are transferred like an office code. These operations are controlled by 11B<SP>1</SP>, which also grounds wire EA instead of LA to indicate the type of code. Completion of connection. The sender is seized in the first place by the grounding of start wire ST by line relay A, which is cut off by relay T when ground is returned on wire CO. After the marker has controlled the extension of the call to the required office and the sender has controlled the numerical selection, ground on wire D energizes D, D1. Subsequently, the ungrounding of wire CO releases T which operates D2 and reconnects line relay A in the reverse sense, whereupon the sender is dismissed. Back-bridge relay CS controls T and hence A to provide supervision.