Patent GB-664241-A (GB)
Title: Improvements in telephonic systems
IPC: H04Q3/00
Filed: 1946-10-08
Abstract: 664,241. Automatic exchange systems. COMPAGNIE GENERALE D'ELECTRICITE. Oct. 8. 1946 [April 1, 1942]. No. 29970/46. Class 40 (iv).  In an automatic exchange system a relay connected in series with a condenser across the line wires of a line circuit responds to alternating current from the line when it is calling and causes the finder of an idle link circuit to hunt for the calling line. Two types of calling impulses are employed. Action in response to a long calling impulse. The impulse of alternating current, e.g. 50 c.p.s. appears across the line 15, 18 (Fig. 2), and relay 2 responds. Relay 3 follows and remains up for the duration of the impulse. Relays 4 and 6 come up in turn the latter releasing the former by short-circuit, whereupon relay 7 pulls up and 4 re-operates. At the end of the impulse 2, 3 and 6 fall away in turn and ground is extended to lead 17 to bring up relay K in the register-controller (Fig. 1). The switch X7 then hunts for an idle link circuit (Fig. 1) in which relay D pulls up in series with H in the register-controller. Relay H cuts the drive of X7, relay G pulls up and the finder N of the selected link circuit hunts for the calling line. On finding, relay E operates to cut the drive, relay 8 in the line circuit comes up in series, and relay G is energized over its lower winding and relapses, the potential of contact T2 thus being considerably reduced to busy the line. Relay 8 releases relay 7 by short-circuit and the release of G brings up L and U whereupon K, E and H fall away. L holds over the contact CX9 of a sequence switch and X7 is homed over bank d. Impulses incoming from the line 15, 18 are, then repeated over contact S2 and pass over a contact X2 of a digit distributing switch to X7 which functions as a digit register. After the impulses have been received the sequence switch (not shown) completes a circuit for magnet P of the link circuit selector. The selector hunts for the outlet marked over wire 101 H pulling up to cut the drive. G is energized over its upper winding and reoperates completing a test circuit over wiper T1. If the line is busy relay E remains down, a circuit for P remains completed over back E and front G, and P steps on. If the line is idle E pulls up and P remains stopped. The lower winding of G is shunted on the upper winding of E, G releases and the line is busied. The sequence switch moves to the selectioncompleted position in which it closes contact BX9 to operate relay C to switch through in the link circuit. The register-controller is then released in known manner. Further impulses received from the calling line are repeated to relay 1 of the called line (Fig. 2) and the A.C. supply wires FF are extended to the line wires to repeat the incoming impulses. Release. Either party sends two long impulses separated by a short interval. Relay 4 is already up so that the action of the first impulse is the same as that described above except that 4 is not operated. At the end of this impulse 3 falls away, followed by 6. Relay 7 however remains up until 3 is reoperated by the second impulse to hold 7 and 4 is then released by short-circuit. At the end of the second impulse 3, 7, 8 and C fall away. Action in response to a short calling impulse. Relay 4 is operated but 6 and 7 are not so that wire 16 is grounded instead of 17. Wire 16 is connected to another register-controller similar to that described and associated with a second group of link circuits. One register-controller may be employed for short-haul traffic and the other for long-haul traffic.