This circuit consists of a stereo audio compressor. We found it in Radio Electronics magazine from October 1968. The circuit uses an opto-coupler made with a neon lamp and LDR.
In the original version of this 1987 circuit, the loads are lamps, but it can be adapted to drive a...
We found this circuit in a Radio Electronics from the 90s. Transistors admit current equivalents,...
This CMOS frequency meter can measure frequencies up to about 1 MHz with a 3-digit resolution. The circuit is...