When the phone rings, a high-powered incandescent light comes on. This circuit can be interesting to obtain the remote call warning or to assist the hearing impaired.
This diagram from a 1967 documentation shows how to switch high voltage neon lamps with 5V TTL...
This semi-proportional temperature control was found in old American documentation. The components are...
Found in a Popular Electronics from the 90s, this circuit makes use of an unusual integrated...