This circuit is from a 1924 book by Gernsback. The receiver uses two tubes and listens to headphones. Power is supplied by battery with the indicated voltages.
This indicator with the integrated circuits CA3162E and 3161E was published in the July 1990 issue...
September 2016 - It can be purchased at Mouser Electronics the new REF6000 precision voltage...
This simple two transistor timer can be used to measure short time intervals. The power supply...