GB1098754A - Telecommunication dialling equipment - Google Patents

Abstract

1,098,754. Automatic exchange equipment. SIEMANS A.G. March 4, 1965 [March 4, 1964], No. 9188/65. Heading H4K. A subscriber's push-button digit sender transmits signals in addition to each digitsignal to indicate depression and release of each push-button. In the arrangement shown in Fig. 1 the additional signals generated at the sub-set N1 are provided by a momentary opening of the line loop. Lifting the handset closes contacts 1GU to complete the line loop and connect the line to an exchange receiving circuit VE. The supply of battery potential to the loop operater relay A1 which by means of its now open contacts 4a isolates the dialling unit S from both the wires. Upon actuation of a dialling push-button T1-T10 common contacts 2TT and 3TT operate, to isolate relay A1, but due to capacitor C, it is slow to release and contacts 4a, momentarily remain open so opening the line loop path through contacts 3TT, dialling unit S and relay A2 to indicate depression of the push-button. The subsequent operation of relay A2 upon completion of the loop isolater relay A1 and the speech circuit M/T from the line at contacts 5a2. With the release of the push-button, contacts 3TT open and 2TT close, but the loop is again momentarily opened at contacts 5a2 of the slow to release relay A2. At the exchange the first momentary break in the loop disengages relay S in the receiving circuit VE which by means not shown operates relay CA to connect the receiving relays in unit WE to the line. Relay N operates to open the line path to subsequent stages. After receiving the digit signal from the dialling unit S the unit WE disconnects itself after a time delay by short-circuiting relay CA. The opening of the line indicating release of the button again disengages relay S to break the holding circuit of relay N, which may also be made to release the unit WE. In another arrangement (Fig. 2, not shown) intended for audio-frequency digit-signalling one of the line wires is grounded throughout the time of depression of the push-button to effect similar switching as above.