This circuit uses an optical coupler to indicate a phone call through a lamp. The circuit is from a Hands-On Electronics from the 90s. The lamp must be incandescent.
This two-port monostable of the 4001 was suggested by an article in the April 1988 Radio...
We found this circuit in a documentation from the 70s. Semiconductors are from the era and can be...
This circuit is from 1992 documentation. The transistor can be a TIP42 with a good heat sink for...