This is the circuit for the HM-10ª, an instrument sold by Heathkit. The circuit is from a Radio Electronics from May 1963. The indication is by an analog instrument.
This circuit was found in the October 1979 issue of Radio Electronics magazine. The circuit is...
This is a conventional differentiator configuration with operational amplifier. In principle any...
This ultra-low power metronome was found in a 1991 documentation. The output transistor is general...