We found this circuit in a Radio Electronics issue from July 1969. The lamp remains on until C1 opens. The time is given by capacitor C1.
This transmitter was found in a 1993 documentation, but it can be assembled with operators like...
This circuit is from a 1997 publication. In it, the circuit uses a light emitter that points to a...
This Meter of Standing Wave Ratio (SWR) was found in a 1994 documentation. The circuit uses only...