SIGNAL PROCESSING UNIT

摘要

A signal processing circuit in a television system for alternatively outputting one of two input video signals, for example a normal video signal and an additional teletext or similar signal, is disclosed. Before the two signals are applied to a signal switching means, their pedestal potentials are equalized by clamping the pedestal potential of one signal to a reference voltage and comparing the pedestal potential of the other signal with said reference voltage and using the comparison signal for a feedback control of said other signal. Also the maximum amplitude levels of the two signals may be equalized by feeding one of the signals through an attenuator having a suitable attenuation factor and having a control input supplied with said reference voltage for attenuating only the A.C. component of said one signal.