This circuit uses components of the time. We found it in a 1968 US documentation. The delay is 100 ns and the input impedance is 1 k.
This circuit, for older machines, fires a second flash with the light received with the first, thus...
This circuit was found in a 90s Popular Electronics. The circuit indicates if a transmitter is working,...
Here is another project that is based on an astable multivibrator, in a demonstration of the...