Signal control circuit in telephone systems - uses common generator and gating unit forming signals of varying frequency

摘要

A common central generator is provided for the subscribers to be connected. Individual signals are produced by a gating device switching on and off the generator frequency. The generator produces a sinusoidal voltage, and the gating device (TE) is connected to it by a line (L), with an amplifier (VE) in parallel with it generating rectangular pulses applied to one input (E1) of a control device (STE), to whose other input (E2) a signal is applied corresponding to the required generator signal. When a pulse rising edge is applied to the first input, potential applied to its second input serves as control potential for the gating device (TE).