This circuit is from a 1969 General Electric manual. The SCR may be the TIC106. Similar circuits from other sources are found on this website.
We found this circuit that uses a thermistor as a sensor from the 1991 Electronics Experimenter Handbook....
This unusual output stage was found in the October 1974 issue of Radio Electronics magazine. The...
This circuit is from a 1998 Electronics Now and can be easily assembled since it uses a common...