Abstract: In a receiver of the type capable of receiving a second or third subchannel audio signal which contains no pilot signal and which is multiplexed with the television audio signal, only the subchannel signal frequency components pass through a band-pass filter the output of which is fed to a clipper circuit so that the carrier level of the output is suppressed. The output of the clipper circuit is detected whether the subchannel signal is present or absent or subchannel signal is increased so that a squelch circuit is turned off and a display device is turned on or vice versa.