This circuit is from a Radio Electronics from October 1963. The transistor is a power transistor of the time, and two transformers are used. The input has 10k impedance and is powered by 12 V.
We found this different configuration that uses a fluorescent lamp as a negative resistance device...
The integrated circuits used in this thermometer are not very common today. The indicator is a...
In the figure we have the way to control a triac of the TIC series with a low voltage through a...