Abstract: A single mechanically adjustable power-frequency control circuit is disclosed which is especially adaptable for use in controlling an audio electrical signal in an automotive entertainment device such as a radio or a tape player. The circuit comprises a parallel resistor and capacitor which are coupled between the wiper arm of a volume potentiometer and one end of the potentiometer by a power boost slide switch. Actuation of the switch couples the resistor and capacitor in parallel with a portion of the volume potentiometer resistance and thereby selectively emphasizes certain portions of the entire audio frequency spectrum of an audio output signal while simultaneously substantially changing the magnitude of the output signal throughout the entire audio frequency range.

Abstract: An improved tape cartridge release assembly for a player/reproducer apparatus of the type used in a vehicle will automatically release a cartridge when the vehicle ignition switch is turned off, will release a cartridge inserted while the ignition switch is turned off, and will release manually as desired. The assembly utilizes a pair of switches operated by insertion of a cartridge to provide identical voltages to the input and common terminals of a semiconductor circuit controlling the release actuator. The semiconductor circuit, by remaining non-conductive, will prevent release until forward biasing voltage is provided to the controlled semiconductor device as by the ignition switch, the manual release button or other means.

Abstract: Public address add-on circuitry to a conventional radio includes a microphone coupled to a preamplifier which draws significant idle current, and is optimally operable when coupled to a proper load resistance. Permanently affixed and capacitively coupled to the audio input stage of the radio is a series element containing a semiconductor junction device and a resistor selected to properly load the microphone preamplifier. When switching from radio operation to public address the quiescent current of the microphone amplifier reduces the resistance of the junction from a high to a low value thereby allowing the preselected resistor to load the microphone. Semiconductor action further disables the tuner portion of the receiver.