Abstract: An electronic volume for effecting a control of an impedance circuit in audio devices or the like includes a variable impedance circuit disposed in a signal transmission path and adapted to vary the impedance in accordance with an electronic control signal. A hold/through gate switchable between a hold state and a through state and adapted to permit, when taking the through state, the input signal to pass therethrough in synchronization with a clock signal of a predetermined period and, when taking the hold state, to hold and deliver the input signal as a control signal to the variable impedance circuit, is connected to a control circuit adapted to vary the input signal supplied to the hold/through gate at a predetermined rate at each time of receipt of the hold/through gate, and a rate changing means is provided for changing the rate of variation of the input signal coming through the hold/through gate.

Abstract: An equalizer apparatus for audio equipment capable of selecting between a 2-speaker system and a 4-speaker system, including a display device indicating proper operation of the control knobs of the equalizer. The display device includes a first illuminable element of a first color for indicating operation of one channel of stereophonic sound reproduction, a second illuminable element of a second color for indicating operation of the other channel of stereophonically reproduced sound, and color coded means corresponding to said first and second colors for indicating which of the control knobs produce data signals for the first channel and which of the control knobs produce data signals for the second channel. Further, the color coded means may indicate which of the control knobs produce data signals for each of the divided frequencies of the respective channels during operation of the audio equipment in the manner simulating quadriphonic sound.