This interesting circuit was found in a 1968 documentation. The transistor can be a general-purpose equivalent. The circuit can act as a shield.
This version is from an old 80's documentation. The SCR can be the TIC106 and the unijunction...
This circuit was found in a 90s Popular Electronics. The circuit indicates if a transmitter is working,...
Is already availablefrom Mouser Electronics is the new reflective B5W-L01 sensor for convergent...