Found in a 90s documentation, this circuit makes use of D1, a switching diode that is uncommon today. D3 is an LED. The circuit monitors 12 V batteries.
This circuit receives the local stations of medium waves listened to in a piezoelectric capsule or...
This circuit was published in an 80's American documentation, but it is still current. The power...
This simple neon lamp power indicator circuit was found in the January 1971 Radio Electronics...