While the earliest wireless equipment was powered by accumulators and plate batteries, equipment that could be operated from mains current soon became available for use at home.
According to the multitude of mains voltages used in Central Europe, voltage switching was often provided for high-quality receivers; usually the voltage 220 V (or 250 V, as the nominal mains voltage today is 230 V) is the correct position.
U.S. equipment manufactured for the home market is equipped with the original 110 V mains transformer and must be operated from the Swiss mains with a 220/110 V transformer or a variable transformer, unless the set was later converted by a radio amateur to the 220 V mains voltage common in Europe - always check before connecting!
Three-phase plugs with a protective earth conductor are used for all modern equipment. The classic sets with two-pole connection should only be operated from sockets with RCD fuse or preferably via an isolating transformer.