This circuit was obtained in a 1970 engineering documentation. The operational is the 741, but other operational ones can be used. The power supply must be symmetrical.
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...