This General Electric circuit produces pulses of light only when light stops shining on the sensor. Equivalent SCRs can be used and the trigger adjustment is done in a trimpot. The maximum load is 40W.
Found in the 1965 Radio Shack documentation, this short-range AM circuit can be built with...
This circuit was found in a 1980s documentation. It is intended for remote vibration monitoring...
This circuit can be found on this website in similar versions. The power supply is given in...