Battery Charge Indicator (CB26002E)

This circuit was found in the March 1997 Electronics Now magazine. It uses a common analog indicator and the transistor is a general purpose one.

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FSK keyboard (CB21758E)
This circuit was found in documentation from 1977. Its purpose is to diode-switch the frequency of a VFO....
AC millivoltmeter (CB21862E)
This circuit is from a 1974 Ferranti transistor manual. The circuit is analog, and the components used...
High voltage source for Geiger counter (CB8478E)
Found in a 90s Popular Electronics, this circuit generates high voltage for radiation detecting...