This is the transmitter for a remote-control system published in the August 1986 issue of Radio Electronics magazine. The circuit uses two 555 CMOS transistors to drive two series LEDs.
In fact, this is the circuit also known as “vox”, that is, a relay triggered by sound. This...
This circuit was obtained from an English magazine from 1976. The signal from the circuit should be...
This receiver for listening on the phone was found in a Japanese magazine in 1967. The circuit uses...