The sensors in this circuit that triggers when the temperature goes out of a certain range are common diodes. The circuit is from the 1991 Reista Electronics Experimenter's Handbook.
We found this circuit in Radio Electronics Special Projects from 1992. The circuit turns on the...
This circuit acts on a relay disconnecting the load when the input voltage exceeds the set limit....
This experimental short-range transmitter came out in a 1972 publication and was designed to...