Abstract: An FM radio receiver, particularly for mobile receivers, reduces the effects of multipath distortion. It selects either an adaptive process (constant modulus algorithm or CMA) or a antenna diversity process depending on the circumstances of the instantaneous reception. The receiver reduces both the decline of the level of received signals with the diversity process and waveform distortion with the CMA process.

Abstract: In a radio frequency communication system in which a radio frequency communication signal is transmitted between a radio terminal (14) and a mobile station (24), it may be that an unauthorized third person uses a scanner-receiver (60) to intercept the communication signal. In order to prevent such an interception, the unit comprises a detecting circuit (30) for detecting an internal signal which is transmitted between a telephone exchange (12) and the radio terminal (14) and is concerned with an ordinary voice signal. The detection circuit produces a detection signal when the internal signal is absent. Responsive to the detection signal, a control circuit (32) controls the internal signal to prevent the interception, as by sending a dummy voice signal whenever the ordinary voice signal is absent.