This double tone generator uses a specific integrated circuit, having been found in a 1977 CMOS Cookbook. The transistors can be the BC548.
From an old manual of unijunction transistors, this oscillator generates different tones when the...
This circuit was found in Radio Electronics magazine from the 90's. The circuit is for small NiCad...
This circuit compresses the dynamic range (amplitudes) of an audio signal. The circuit is passive and...