Arrangement for applying a ringing voltage to a subscriber's line

摘要

When electronic circuits are used for applying a conventional ringing voltage which has been superimposed on the conventional supply voltage, they require a high supply voltage. According to the invention an a.c. voltage is used in which that portion of each period in which the polarity is positive differs from the portion in which the polarity is negative. This a.c. voltage has a DC-component by means of which the condition of the subscriber's loop can be detected. The peak-peak value of the ringing voltage may be twice the maximum permissible voltage swing of a wire of the subscriber's line, which is an optimum.