Patent GB-680904-A (GB)
Title: Improvements in or relating to automatic or semi-automatic telephone systems
Inventor: JONES ERIC WYN
IPC: H04Q3/00
Filed: 1949-07-07
Abstract: 680,904. Automatic telephone systems. AUTOMATIC TELEPHONE & ELECTRIC CO., Ltd. June 7, 1950 [July 7, 1949], No. 17936/49. Class 40 (iv). A selector is seized over a V.F. junction by the first impulse of the digit train, the digits being stored by a mechanical impulse regenerator and repeated after an interval sufficient for preparing the selector. In response to a trunk offering signal, the incoming relay set reverts a V.F. pulse and, before conditioning the selectors for trunk offering, awaits a further pulse from the outgoing relay set, this further pulse confirming that the signal originated from an operator's position. The outgoing relay set is available to operators manual boards and to a group selector multiple. Two signalling frequencies are used, one for each direction. Both the relay sets are suitable for use at a tandem exchange to provide end-to-end signalling. Setting up a connection from the manual board MB or group selector multiple GSM, Figs. 1, 2. Closure of the incoming loop brings up A and B follows to complete circuits for Q, J, N, JA. In response to the first digit, AA sends impulses of 2500 c.p.s. over the go pair - 1, + 1. The dialling relay C at its contacts c4 prevents distortion of the impulses and for the duration of the digit releases Q, the relay controlling the connection of the return pair -2, + 2. At the incoming relay set, Figs. 3 to 5, BA repeats the impulse train to the registering magnet RM of a mechanical impulse regenerator MIR similar to that described in Specification 458,095. Relay BB closes the loop to seize the incoming group selector, releases a normally operated relay K to energize KR, and connects up BC which earths the marking magnet MM of the regenerator MIR. Relays BB, BC complete circuits for the operation of IP, BCA, respectively, followed by IS, F. At the end of the digit, BA disconnects BC, whereupon the marking magnet MM releases to prepare the regenerator for transmitting the digit. The resultant closure of the marking magnet contacts MMC completes a circuit for BY to connect the impulsing contacts IMP to the outgoing loop, the loop being held by IP while BY operates. DX follows slowly for IP, IS to release in succession, whereupon the regenerator transmitting magnet TM opens contacts TMC to release DX and to allow IP, IS to re-operate, thereby releasing TM. While the digit is being repeated by contacts IMP, the circuit of DX is maintained open at CP, RP. The cycle of operation of the sluggish relays DX, IP, IS serves to ensure adequate delays before and between transmission of the digits, in spite of the regenerator being able to receive and transmit simultaneously. When all the digits have been repeated, the off-normal contacts N open to release BY, which is followed by IP, IS. Answer. Shunt field relay BD brings up DA to disconnect the impulse regenerator MIR and S follows to send back a 2400 c.p.s. answer signal. IS, DB operate in turn to disconnect S so terminating the 100 m.s. answer signal. IS releases and M is operated to prepare the terminating network for speech. At the outgoing end, D, E operate and Q releases for the duration of the answer signal. E brings up P which shunts a sluggish relay N and unless the signal responsive relay D releases within a predetermined time, N falls back to complete a circuit for an alarm relay PG. PG locks up, lights an alarm lamp LP, busies the junction, reverts N.U. tone and disconnects DD. Otherwise, when the answer signal ceases, DD prepares the terminating network for speech, reverses the line potentials and connects metering lead 10 to effect metering if the call is of local origin. Earth over rectifier MRA maintains the guarding condition, while DD changes over. Relays J, JA release. Trunk offering. This is effected by the actuation of a key at a manual board MB to apply potential to one of the line conductors, whereupon OC connects up AA to signal forward. At the incoming end, the signal operates BA, BCA falls back to bring up BCB, which shunts the regenerator impulsing contacts IMP, and S during the release period of F sends back a pulse of the signalling current. At the outgoing end, the backward pulse causes D to release Q and operate E followed by P, whereupon AA falls back to terminate the original trunk offering signal. At the end of the backward pulse when D, E release, DD reverses the line connections to actuate a supervisory signal and J, JA release. A circuit for OD is completed by J over a make contact of OC, and J, AA are operated to send a confirmatory pulse forward. If the trunk offering signal had originated from somewhere other than the manual board, OC would have been back and the circuit for OD incomplete. The operation of BA in response to the confirmatory pulse completes a circuit for the left-hand winding of BCA which earths the line wire-to bring about a trunk offering condition in the final selector. To re-ring the required subscriber the operator again unbalances the line wires for relays OC, OD, J, AA to operate in succession, after which J, AA fall back. A pulse of signalling current is thus sent over the junction to cause BA to connect up BCA, whereupon earth applied to the line wire initiates ringing. Release. If the caller clears first, the release of A operates C and releases B, Q followed by P, N. The guarding earth is temporarily removed by B to release the preceding equipment. The release of B connects up E, J, AA, to send a continuous clear forward signal over the junction and shunts down C which replaces the guarding earth. The operation of BA at the incoming end by the clear forward signal releases BCA followed by BB, F, and S operates to send a continuous clear back signal which causes D to disconnect J, whereupon the outgoing relay set returns to normal. When the clear forward signal ceases, the incoming relay BA falls back to operate DA, DB. Release of the succeeding selectors removes the shunt on K which disconnects KR, S in turn so that the clear back signal is terminated and the incoming relay set returned to normal. If the called party clears first, BD, DB release in turn and S, IS, DB interact to send back pulses of the signalling current. At the outgoing end, D, E operate to disconnect DD, thereby actuating the supervisory signal. When the operator or caller clears release takes place as described above. Busying junction from the incoming end. Key KB when actuated connects the signalling current to the junction and so busies the outgoing relay set. If the incoming relay set is mounted on the jack-in principle, a V.F. current is automatically connected to busy the junction when the relay set is removed.