The time of this timer depends on C1. The circuit was found in the July 1994 Electronics Now magazine. The supply voltage depends on the relay and can go up to 12 V.
We find this circuit in a 1980s documentation for amateur radio. The circuit shows how to switch...
Suggested by a 90s EDN, this circuit supports almost any LED as a source and a phototransistor as a...
This transmitter for the 2-meter range with a power of 1.5 W was found in a magazine 73 for radio...