This circuit is from a 90's documentation. The circuit is simple, as it uses only two transistors, and the control is done by pressure switches. The indication is done by LEDs.
This is the basic configuration of an operational amplifier sample & hold circuit. The FET and...
Found on 80's Popular Electronics, this circuit uses an uncommon integrated today. Programming is done...
Found in a 1968 Mullard manual, this circuit can function as an infrared audio link. The...