This circuit is from a 1975 RCA tube manual. It appears elsewhere on the site. R5 depends on the voltage of the amplifier with which it is used and can be changed.
This moisture-activated relay was obtained from an American documentation from the 1980s,...
Found in an old American publication, this circuit indicates the direction the antenna is pointing in...
We found this circuit in Radio Electronics magazine from August 1984. The circuit aims to control the...