A control unit is inserted in the power lines that serve a vehicular telephone and an audio system. A power monitoring circuit detects current increases related to operation of the telephone, either from an incoming "ring" signal or the "off hook" condition in preparation for an outgoing call. The monitoring circuit generates a control signal which is applied to an electronic switching circuit that interrupts the flow of power to the audio system circuits. So long as the telephone is in use, the audio system is disabled. When the telephone returns to the quiescent or stand-by state, the current drawn by the telephone drops substantially below a threshold level of the monitoring circuit and the switching circuit restores the power to the audio system.

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.

An output transducer and amplifier are shared between an audio system and a cellular Phone in an automotive vehicle. An interface arbitrates between the program audio signals and the phone audio signals to select or deselect each of the audio signals depending on the status of each audio source. When only one source is in use then normally the audio signals from that source are selected. If both sources are turned on but a phone call is not in progress, then audio signals from both sources are simultaneously presented to the output transducers after summing. When a call is in progress, only the phone audio signals are selected.

A device for controlling an accessory based on the detection of transmissions of appropriate input frequency exceeding a minimum threshold amplitude from a nearby cellular telephone. The device includes an independent receiver for directly detecting the transmissions from the nearby cellular telephone and a controller connected to the receiver for controlling the accessory device based on the detection of the transmission from the nearby cellular phone. The independent receiver includes a frequency discriminator of a totally digital design for detecting a signal which is greater than a predetermined threshold frequency and amplitude.

Apparatus and a method for temporarily disabling the operation of a noise-producing electrical device or internal combustion engine upon detection of a predetermined awareness condition, such as an incoming telephone call, doorbell ring, security system alarm or other awareness condition. For disabling operation of an electrical device, the apparatus includes a command module and one or more switchable power receptacles that respond to a control signal from the command module, de-energizing the electrical device, when at least one of the predetermined awareness conditions is detected. Control signals are communicated to the switchable power receptacles via either a radio frequency signal, or by a modulated signal that is conveyed over an alternating current electrical power circuit to which the command module and switched power receptacle(s) are connected. For disabling operation of an engine, the apparatus includes a command module that sends a wireless signal to a shutdown module to control operation of the engines ignition or fuel systems, so that operation of the engine is disabled when the shutdown module is switched to a shutdown mode. Disabling operation of a noise-producing device enables a signal that is produced in conjunction with the awareness condition, such as a telephone or doorbell ring, to be more easily perceived.