Two-component photorelay (CB22087E)

This circuit makes use of an ultrasensitive relay or reed-relay. LDR supports equivalent.

Current Limiting Battery Charger (CB19020E)
Some of the components used in this circuit are not very common today. The circuit is from a 1996...
Quadrature detector (CB21753E)
This circuit was found in a 1977 American manual. The integrated circuit is from the time....
Superheterodyne FM Receiver (CB4334E)
The integrated circuits used in this 1989 project are uncommon today, including the IF coil that...