Found on a 1964 CQ this circuit is intended for tone frequency change modulation (FSK) telegraphic transmissions. It operates with signals of 2.975 and 2.125 Hz.
This thermal control circuit appeared in Radio Electronics magazine in October 1958. The circuit is...
This small medium wave radio was manufactured in the 1960s in Japan. The circuit is powered by 4...
This circuit is from a 1988 publication. It makes use of an LM3914 LED driver circuit, still...