This circuit was obtained from an old American documentation, and practically any general-purpose transistor and sensitive relay can be used according to the supply voltage.
Found in the September 1984 issue of Radio Electronics magazine, this circuit uses common...
Found in the July 1968 Supertena Bulletin of a Popular Electronics, this receiver makes use of the...
This intercom for the 27 MHz band was found in a recent English documentation, working with a...