We found this circuit in a 1980s documentation. Equivalent components can be used. The circuit senses temperatures in the range of 0 to 50º C and uses a transistor as sensor.
This reflex receiver for the mid-wave range employs germanium transistors of the time. We found it in...
The resonant circuit depends on the crystal frequency that can go up to a few megahertz. The...
The frequency of the square signal produced by this circuit depends on the light falling onto the...