Screw-in sockets with bulb socket, around 1920

 © Technisches Museum Wien, Photo: Peter Sedlaczek

The screw-in socket also used to be called an “electricity thief”. It enabled the use of the so-called “lighting current” for other purposes without payment.

When electrification first began, buildings were predominantly only equipped with light cables. Any other electric consumption was not intended for or not yet available. Therefore, most homes did not have any sockets. Billing took place without a meter reader, since the power consumption was calculated for one light source per room and a flat rate was determined. Screw-in sockets were screwed into bulb sockets and enabled the additional connection of electric appliances. Thus, electric appliances could be operated in places where no sockets were available.

One of the first important domestic electric appliances was the electric iron. Similar to electric light, it reduced the workload immensely. In most cases, it could only be attached to the so-called “light cable” via a screw-in socket. This consumption was not included in the flat rate.

The Technisches Museum Wien (Vienna Technical Museum) exhibits a screw-in socket from the Siemens-Schuckert factory in Vienna from the time period around 1920. Its Edison screw thread E-27 fits in all corresponding bulb sockets. It provides a bulb socket to connect a light bulb and two double-pole sockets to connect appliances.

With increasing electrification and the standardization of the initially different power networks, meter readers were soon installed and flat rate bills came to an end.

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