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.
The circuit shown is from the Texas Instruments optoelectronics manual, applying to low power...
This circuit was found in a 1968 General Electric documentation. It has an input impedance of 2 M ohms...
This filter that rejects a frequency range determined by the double-T was found in the August 1993...