This crystal oscillator generates a 20 MHz signal. Equivalent transistors such as BF494 and 2N2222 can be used. The stabilizing diodes can be 1N4148.
This voltage calibrator circuit using a zener diode was found in Radio Electronics magazine from...
The relay of this circuit closes when the position set in P2 is reached by the sensor...
The purpose of this circuit, which we find in an old American documentation, is to allow the...