Powerful IR Emitter (CB26030E)

This modulated circuit was found in the November 1997 Electronics Now magazine. The power transistor can be any MOSFET,

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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...