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 simple signal injector oscillator was found in a 1981 documentation. The coil can be made...
This variable oscillator was found in a Mullard transistors manual from 1960. The resistor R5 is...
This circuit is from an American 80's documentation. The circuit indicates when the voltage of a 9 V...