This circuit operates from 20 Hz to over 20 kHz and is easily tunable. We found it in a 70s documentation. The circuit can be implemented with modern operational amplifiers.
The purpose of this 1985 circuit is to make the sound test of type 106 SCRs (MCR106, TIC106,...
Using the CMOS 4001 we found this circuit in the October 1974 Radio Electronics magazine. The...
We found this circuit in a 1957 Raytheon transistor publication. The circuit can be assembled with...