Abstract: A system for installing a radio audio amplifier in a vehicle at a location remote from the vehicle radio. The system senses voltage in the radio speaker wires to turn the amplifier on and off.

Abstract: An active noise conditioning system for use with a combustion engine exhaust system is provided. A controller receives an exhaust noise signal, along with various other feedback signals for producing an anti-noise signal in response to the input signals. An amplifier is provided for receiving and amplifying the anti-noise signal. A wave generator receives the amplified anti-noise signal and generates an audio anti-noise signal. The output of the wave generator is collocated with the exhaust pipe of the exhaust system, where the audio anti-noise signal and the exhaust noise are acoustically coupled, which effects cancelling of the exhaust noise.

Abstract: An electronic Class B master power amplifier is cascaded with a like slave Class B electronic power amplifier between ground and an output terminal to which the output of the slave amplifier is connected. A first pair of D.C. sources deliver potentials of magnitude V.sub.ss but opposite polarity to the master power amplifier and each have a reference terminal connected to ground. A second pair of D.C. sources deliver potentials of magnitude V.sub.ss but opposite polarity to the slave power amplifier, and each have a reference terminal connected to the outupt of the master amplifier. A common input signal to be amplified is delivered to the inputs of the master and slave amplifiers.