This 1969 circuit uses a 117 V filament tube powered directly by the power grid. The original circuit makes use of a charcoal microphone, a common component at the time.
This circuit was found in documentation from the 1980s. The integrated circuit used is uncommon today...
This audio oscillator configuration appears in many of our circuits and even in this section from...
This Linear Technology circuit charges a battery from the energy produced by a wind generator that can...