Patent GB-584572-A (GB)
Title: Improvements relating to automatic telephone systems
IPC: H04Q3/00
Filed: 1945-01-04
Abstract: 584,572. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., and LONG, D. P. Jan. 4, 1945, No. 333. [Class 40 (iv)] In a system in which a marking switch controls the advance of a single motion selector switch which then hunts for an outlet or one of a group of outlets marked in accordance with two digits, the dialling relay is operated over a terminal of the selector when it is seized, is released at the end of the first digit to allow the selector to drive to a preliminary position and is there re-operated prior to reception of the second digit. The invention is described as applied to a group selector, Fig. 1, which hunts over a selected group in response to one or two digits, and to a final selector, Fig. 2, which gives access to individual and P.B.X. lines. Both selectors may be of the type described in Specification 378,585. If the selection is made in response to two digits, the selector has a preliminary contact position at the commencement of the arc containing the desired outlet, but if a group selection is made in response to one digit only, the marking is applied to the appropriate group of outlets. Group selector, Fig. 1. Upon seizure, line and release relays A, B energize, followed by dialling relay C, the circuit for the last relay including the left-hand winding of relay H, wiper P1, test relay T, wiper G1 and wiper MA1 of marking switch MA. Relay T energizes and connects up the opposing right-hand winding of relay H to prevent its operation. The first digit sets the marker MA in the usual manner, T being released and C being held over its lower winding during the digit, after which C falls.back and connects up the magnet MU to drive the selector..Groups of outlets denoted by a single digit are wired to the full line banks and are marked directly over MA1 and if the received digit indicates such a group, the selector immediately hunts for an idle outlet in the usual manner. If a second digit is necessary, however, to determine the group, the selector moves to the appropriate preliminary position, which is marked over MA1 and MB1 or MB2, where C re-operates in series with T. The second digit sets the marker MB and on the relapse of C the selector is restarted to hunt over the selected group, which is now marked over MA1 and MB1 or 2. Relay T energizes on an idle outlet and connects up switching relay H, but if no idle outlet is found, the selector continues to its last position in which T energizes in series with C, H being inoperative, and busy tone and flash are applied through relay A. It should be noted that wipor switching relay WS is controlled over crossconnections to banks MA2, MB3, MB4, while banks MA3, MB5 control the connection or non-connection of earth to the + wire to discriminate at the final selector between pairs of hundreds digits that denote the same outlet group. Final selector, Fig. 2. Six single wiper marking banks of the selector are cross-connected to banks MB1 ... 5 of the units marker MB, one of which is selected by the setting of the tens marker MA. Individual lines and first lines of P.B.X. groups, are marked in banks G1, G2, while P.B.X. lines other than the first are marked in banks GW1, GW2, GX1, GX2. Wiper switching relay WS is dependent on the discriminating signal mentioned above. After the tens digit is received, the selector advances to the beginning of the appropriate bank under the control of marker MA, as in the group selector, whereupon dialling relay C re-operates in series with T in readiness for the reception of the units digit. Specification 417,461 also is referred to.