This thermostat circuit triggered by a neon lamp and having a thermistor as a sensor was found in an old American documentation. SCR is according to load.
We found this circuit in an 80's Radio Electronics. It can still be easily assembled as the used...
In the figure we have the way to connect two high power operational amplifiers LM12 to double the...
This frequency modulated light transmitter is from a 1990s documentation. The circuit may use...