Audible Voltmeter (CB21395E)

This circuit was found in an American publication from 1969. Transistors are from the time and can be replaced by modern equivalents.

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Amplification Stage (CB6178E)
This small signal amplifier circuit was found in Motorola's 1969 documentation. The FET and the...
Electric fence (CB6231E)
This circuit was found in an American 80's circuit board. The components used are current except the...
Power Grid C with Optocoupler (CB16025E)
With an optodiac we have the circuit of the figure, suggested by MotoroIa, in which we do the...