Abstract: A telephone-operated stereo shut-off device for a stereo comprising a sensing component operatively associated with a telephone to sense an increase or decrease in voltage when the telephone rings, is answered or hung up. The device consists of a signal transmitting component that transmits a signal indicating the increase or decrease in voltage when electronically activated by the sensing component; a signal receiving component for receiving the signal transmitted by the radio transmitting component; and a switching component for opening and closing a speaker muting circuit located between a speaker and the stereo. The switching component is activated by the signal receiving component, wherein the speaker of the stereo is muted when an incoming telephone call is answered and conversely the speaker resumes operation after the telephone is hung up.