This circuit was found in an ancient American documentation. The power supply is not given, but we have the voltages used. The relay is sensitive type for high voltage.
This transmitter was found in an old publication on espionage. It applies a signal of a few...
This Motorola circuit uses only one transistor. The circuit is from 1965 documentation. The...
This circuit is from a Poptronics, American magazine of August 2000. The circuit can be assembled with...