A squelch circuit for a radio transmitter/receiver includes an amplifier, a digitally-controlled electronic volume control, a volume adjusting variable resistor, and a volume controller. The amplifier amplifies a received audio signal input and provides the received audio signal to a loudspeaker. The digitally-controlled electronic volume control changes the output level of the amplifier. The volume adjusting variable resistor outputs data representing a volume value. The volume controller constantly detects changes in volume value data output from the variable resistor, and controls an attenuation amount of the digitally-controlled electronic volume control in accordance with the volume value represented by the variable resistor. While in a "mute" state, this volume control continues until a predetermined time has elapsed since the detection of the change in volume value data. The volume controller then sets the attenuation amount of the digitally-controlled electronic volume control to an infinite attenuation amount.