This circuit was found in a RE Experimenter Handbook from the 90's. The components are of the time, rare nowadays, except the 555 and 4017.
This circuit was obtained from 1967 documentation. It uses a sensor to determine the trigger...
Found in a 1980s publication, this circuit uses an operational amplifier from that time. The...
Found in an old American publication, this circuit indicates the direction the antenna is pointing in...