Abstract: A television receiver includes a volume control circuit (4) for controlling levels of sound signals corresponding to a left channel, a right channel, a center channel and a surround channel and speakers (6 to 10) corresponding to these channels. The television receiver further comprises a test tone circuit (11; 18), a microcomputer (14) and a character display circuit (16). The test tone circuit (11; 18) supplies a test tone of a prescribed frequency sequentially to the speakers (6 to 10) through the volume control circuit (4). The microcomputer (14) provides a command to the character display circuit (16) so that a CRT 17) displays which speaker is currently supplied with the test tone as well as volume levels of the respective speakers.

Abstract: A surround-decoder comprises terminals to which left and right stereo input signals are applied, a decoder for processing the left and the right stereo input signals to provide left and right stereo output signals, a center output signal and a surround output signal, circuits for detecting the left and the right stereo input signals to be monaural signals, and a switch responsive to an output signal of the detecting circuit for cutting off an output of a surround signal from the decoder.