We found this configuration in a 70s American documentation. The circuit makes use of operational amplifiers of the time. Modern equivalents can be tested.
This circuit came out at a Wireless World in January 2000. The circuit can be easily assembled as it uses...
We found this transmitter circuit for different frequency ranges in a 1992 documentation. The...
This TTL circuit can be used as a shield, controlled by one of the inverters. The circuit must be...