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 capacitive sensor that operates with a high frequency oscillator was found in Radio...
This amplifier for the experimenter´s bench source 1 W and uses germanium transistors but can be...
This circuit was found in a Hands On Electronics from the 90s. The microphone is a small 75-ohm...