This basic relay configuration was found in a July 1994 Electronics Now. The relay is supposed to be sensitive, and the times are changed by changing C1.
This circuit is from Radio Electronics. The magazine no more exists, but the circuit can be...
Found in a 1990s US publication, this alarm circuit detects when a light beam is interrupted. Optical...
This telephone circuit was found on a 90's EDN. It keeps a flashing LED to indicate that there was a...