Silent alarm (CB22471E)

This circuit is from a Popular Electronics from 1992. The circuit powers an LED when triggered.

Optical receiver (CB20697E)
Found in an American documentation from the 90s, this circuit works as a receiver for a data...
5 W Amplifier with Germanium Transistors (CB14765E)
This experimental amplifier was found in the 1960 Mullard transistor reference manual. The...
Resynchronizer Circuit (CB20096E)
This circuit makes use of an uncommon TTL component today, but it can be implemented with...