Found in a 1924 documentation, this circuit is powered by 3 batteries, two of which are high voltage. The output is a high impedance headphone jack.
This circuit was found in 1980s Radio Electronics. The circuit includes the power supply. The...
This circuit was found in a former Popular Electronics. The timing is set on the potentiometer and the...
This circuit has appeared on our site several times as a battery status monitor. In this...