EVALUATION CIRCUIT FOR ALTERNATING VOLTAGE PULSES

摘要

The invention relates to a detection circuit and to a method for detecting alternating voltage pulses of a defined frequency. According to the invention, an input signal is firstly transformed into a low-frequency signal by multiplying this signal with a beat frequency. This signal that is reduced by mixing can then be filtered and evaluated. The circuit is particularly suited for identifying the charging unit signals of the telephone network.