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.
We found this circuit in a 1995 paper. The reed switches are surrounded by a few coils of coarse...
This circuit can supply voltages in the range of 8 to 20 V with a maximum current of 3 A. The...
If mounted with SMD components, this spy transmitter for the FM range can fit into a pen. The...