Abstract: A compact portable stereo headphone amplifier system for use with a conventional stereo audio source, such as a cassette or compact disc player, in which components are located on both sides of a circuit board and in which left channel components and right channel components are located on opposite sides of the circuit board thereby providing a compact unit.

Abstract: A system for measuring changes in the resistance of a living body includes a resistance measuring circuit, an amplifier circuit and an indicator circuit in which the amplifier circuit includes a calibration circuit to give a generally constant amplitude response to a given measured input. Radio frequency insulators are included to reduce noise in the system. The circuits are operated such that when an overall change in the resistance of a living body occurs, the resistance measuring circuit is adjusted to determine the overall resistance. To account for changes in sensitivity caused by the overall change in resistance, the gain of the amplifier circuit is automatically adjusted to thereby maintain a generally constant amplitude response.