Method for detecting SECAM television signals and circuit suitable therefor

摘要

A circuit for detecting SECAM television signals for a compatible multi-system colour television receiver contains a gate circuit (8) for passing at least one component of each colour subcarrier of a received colour television signal, as a function of a gate pulse, to a band-pass filter (16) having a pass-band centre frequency which is tuned to the trough of the characteristic spectrum, provided with peaks and troughs, of a colour subcarrier of the SECAM system so that the output signal of the band-pass filter occurs at half the line rate if the received signal is a SECAM colour television signal. A frequency discriminator (18) outputs a signal which indicates the reception of a SECAM signal if it detects an output signal from the band-pass filter, occurring at half the line rate, for distinguishing between colour television system signals of other systems such as NTSC and PAL. <IMAGE>