SIGNALISIERUNGSEMPFAENGER.

摘要

To extract signal frequencies transmitted on a telephone line (a,b) the signal input (E) is connected first to an attenuator (DG). A high pass filter (HP) on the attenuator output side is connected to a control pulse input (TL). The filter output is extended to a signal evaluator and converter (SE) whose output, in turn, is passed to a band-pass filter (BP). A band width changing circuit (BU), also controlled by the pulse input (TL), is connected to the band pass (BP) and the attenuator (DG). The threshold frequency and the band centre frequency of both filters (HP, BP) is set by the control pulse (TL) to the desired value by setting the appropriate pulse frequency. The threshold frequency is lower than the band centre frequency.