Found in a 80s American documentation, this circuit pulses a lamp for optical relay tests. The circuit can be modified to trigger a high brightness white LED.
This circuit, from a 1994 publication, shows how to polarize a phototransistor to receive...
This simple current control setup was found in documentation from the 60's. The low current...
This circuit generates frequencies determined by R3 and C1. We found it in the Radio Electronics magazine...