This simple circuit makes use of neon lamps to indicate the voltage of a power grid. The lamps are common neon and the circuit indicates whether the voltage is 110 V or 220 V.
This circuit was obtained in a 1975 documentation. The maximum frequency depends on the diodes and the...
In the figure we have the basic configuration of an operational amplifier for AC signals using the...
This traditional signal injector from a 1970s publication uses germanium transistors. We can mount it...