Dolter system

The stud contact system is a once-obsolete ground-level power supply system for electric trams. Power supply studs were set in the road at intervals and connected to a buried electric cable by switches operated by magnets on the tramcars. Current was collected from the studs by a "skate" or "ski collector" under the tramcar. The system was popular for a while in the early 1900s but soon fell out of favour because of the unreliability of the magnetic switches.

In recent years the concept has made a comeback, to remove overhead supply systems from scenically sensitive areas. Current manufacturing methods and electronic control means such systems are much more reliable. The new tram system in Bordeaux, France has resurrected the system in the form of Alimentation par le sol for aesthetic reasons in the city centre.

Power supply studs are the fixed contact elements of a stud/skate or stud/ski collector electrical connection system. They are used when a moving element needs to be in electrical contact with a static element. The main advantage of the system is the self-cleaning facility of the skate/ski with the stud.

The stud contact system or surface contact system was used with some tramway systems. It is used especially where an overhead system would be obtrusive. As the studs would be on open roads rather than special track, methods have to be adopted to ensure that they are only live when under a vehicle. Early systems used mechanical switches. Most use magnetic activation from a magnet on the vehicle, but a few used a purely mechanical system. Systems in use in the early part of the 20th century included the Lorain, Dolter, and GB surface-contact systems, which were all magnetically operated, and the Robrow surface-contact system, which was mechanical. In practice the technology of the time could be erratic. This meant studs that that did not make contact when activated, and studs that remain live after the vehicle had passed over. Consequently the systems tended to be replaced with either overhead systems, or continuous contact sub surface systems.

Most electric railway systems take the power from an external generator. This means the electricity has to be collected while the locomotive is on the move. In this context a locomotive refers to any electric vehicle on a railway track or tramway track. Other than railways the other most common system of electrically powered guided transport is a tramway system.

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Wikipedia