If you have the skills and can get your hands on SMD components, you can assemble this small amplifier. We found it in the Radio Electronics Experimenter special edition from 1990.
This is the circuit for the HM-10ª, an instrument sold by Heathkit. The circuit is from a Radio...
This circuit indicates when the monitored voltage drops below the value determined by the divider...
This circuit, from a 1975 Motorola manual, uses a power Darlington transistor of the time. We can...