PURPOSE: To obtain an identity discriminator which reduces the integration time and improves the discrimination surely, by providing a means for detecting the deterioration of sound signals, relating to a car radio receiver having two reception system.

CONSTITUTION: Detectors 38, 39 of an identity discriminator detect output sound signals of low pass filters 30, 31 and provide a signal corresponding to the sound signal level, and voltage comparators 40, 41 compare the output of the detectors 38, 39 with a prescribed comparison level and provide whether or not sufficient sound signal level exists for the identity discrimination. This signal is called as a sound level discrimination signal and referred to as "effective" when a sufficient sound level exists and as "ineffective" when insufficient. The two sound level discriminating signals are given to a controller 17 together with a content discrimination signal, i.e., the output of voltage comparators 36, 37, and the controller attains discrimination.