This two-tube circuit, one being a double, was found in Radio Electronics magazine from July 1958. The distance to the microphone depends on noise and losses. The cable must be shielded.
An OR gate can be implemented with an LM3900 transconductance operational amplifier. The circuit is...
This traditional relay configuration, found in old documentation, is intended for 2A relays for...
This simple radio circuit was obtained in a Japanese publication in 1967. The circuit uses...