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The Stud Contact System is a once obsolete ground-level power supply system for electric trams. 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. However, the new tram system in Bordeaux, France has resurrected the system in the form of alimentation par sol for aesthetic reasons in the city centre.
The Brown Surface Contact System was manufactured by Lorain.
The Diatto stud system was the most common in France, with over 20,000 studs in use. It was invented by an Italian, Alfredo Diatto of Turin and was first installed in Tours in 1899, followed by four of the Paris tramway companies in 1900. Whether Alfredo Diatto was connected with the Diatto car company is not known .
For the Dolter system a conductor cable was laid in a trench between the rails. At 9-foot (2.7 m) intervals a box was fitted between the rails that contained a stud (which protruded about 1 inch (25 mm) above the road) and a bell crank. A magnet on a passing tram attracted this crank which then moved to make contact between the conductor cable and stud; once the tram moved away the crank dropped away and the stud was no longer connected to the cable. A long skate was suspended beneath each tramcar which was magnetised by electro-magnets and so both operated the cranks and collected the current that both moved the tram car and powered the electro-magnets. A small battery was carried to charge the electro-magnets should the power be interrupted. The negative return current passed through the rails.
The town council of Torquay did not want their seaside resort disfigured by the poles and overhead wires of a conventional electric tramway and so invited the Dolter Electric Traction Company to construct a tramway using their stud-contact system. A horse was killed after it stepped on a live stud during construction of the Torquay Tramways. Each tram car was then fitted with a bell connected to a special contact arm to warn the driver if a stud remained live after it had passed. The conductor of the tram then had to reset the crank using an insulated mallet. During the Board of Trade inspection of the tramway four such studs were detected during about 8 miles (13 km) of tests. There were also frequent problems with trams being stopped when a stud failed to be made live when needed. The network covered 6.79 miles (10.93 km) and opened in stages during 1907 and 1908. On 27 January 1910 a snow storm stopped all the trams as they couldn't make contact with the studs. It was converted to overhead collection in 1911 shortly before it was extended to Paignton where the town council had refused to allow the Dolter system to be used.
A short Dolter system also opened in 1907 in Hastings along the seafront to connect two sections of a network that otherwise used overhead collection. It lasted until 1913. For the next eight years the trams that worked along Hastings sea front were fitted with a small motor to enable them to move between the two sections of overhead wire, but in 1921 wires were provided along the section.
The Mexborough & Swinton Tramway used the Dolter system from 1907 until 1908 when it was converted to overhead supply.
Ansaldo an Italian based manufacturer of rail related items has introduced an updated system under the name Tramwave. The centre track is a strip of contact strips with only a small gap. Under the track is a ribbon which is lifted by a magnet on the moving vehicle. Only the contact strips under the moving vehicle are live. Power is collected by a long shoe collector, skate collector or ski collector.