This high impedance circuit was found in 1967 documentation by Ferranti. The original operational amplifier is from that time. The circuit can be implemented with modern equivalents.
This blocking oscillator configuration was found in a 1964 American book. The circuit can be...
This low power circuit for the FM band was found in a spy book from the 90s. The tunnel diode is...
This transmitter, indicated for espionage applications, is permanently powered by the power grid....