METHOD AND APPARATUS FOR THE DETECTION OF A TRANSITION OF THE DIRECT CURRENT COMPONENT OF A PERIODIC SIGNAL, IN PARTICULAR FOR SUBSCRIBER LOOP INTERFACE CIRCUITS

摘要

The method includes generating a binary signal (S4A to S4D) which is time modulated. To do this, an alternating signal (S1) is compared with a known cyclical signal (S5) and a threshold signal. There is measured the durations between the transitions of the modulated signal by means of a high speed clock and by means of counting in the positive and negative directions of the clock pulses for one or more periods of the signal under examination. If, after counting, a residual value is found, one generates a binary signal representing the transition.