Level Adjustment of Audio Signals by Means of a Solid-State Electronic Attenuator

A solid-state centralized system of level adjustments of audio signals is described. The problem considered was how to adjust and vary the level of audio signals with the same precision achieved with present mechanical step-attenuators. The method finally decided upon was that of using the variable-impedance characteristic of a forward-biased diode. The diode impedance decreases proportionately to the forward direct current flowing through it.