This circuit triggers a relay when the set temperature is reached. The circuit is from an old documentation. The relay may be equivalent according to the transformer secondary voltage.
This circuit is from Radio Electronics magazine from June 1958. The tuned range at the time was...
Found in Popular Electronics from the 90's, this tuned to infrared modulated receiver uses a PLL....
This circuit was found in the March 1979 issue of Radio Electronics magazine. Integrated circuits must...