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.
This circuit of a good amplifier for domestic use is from the Philips Databook of 1990. The...
We found this circuit in an old American documentation. The components are from that period and...
Found in 90's Electronic Engineering, this circuit produces a pulse with a delay that depends on R3...