Technology
Ground-level power supply is used, primarily for aesthetic reasons, as an alternative to overhead lines. It is different from the conduit current collection system which was one of the first ways of supplying power to a tram system by burying a third and fourth rail in an underground conduit (‘vault’) between the running rails. Conduit current collection was used in historic tram systems in Washington, Manhattan, Paris, Berlin, Marseilles, Vienna, Budapest and London. It fell into disuse because overhead wires proved much less expensive and troublesome for street railways and because in Manhattan, Paris, Washington and West Berlin all trams were replaced by buses for reasons unrelated to the power supply issue. In Prague on the Charles’ Bridge (Karlův most) a system invented by František Křižík was used, similar to today's APS.
Unlike the track-side third rail used by most metro trains and some main-line railways, APS does not pose a danger to people or animals and so can be used in pedestrian areas and city streets.
APS uses a third rail placed between the running rails, divided electrically into eight-metre segments with three-metre neutral sections between. Each tram has two power collection skates, next to which are antennas that send radio signals to energise the power rail segments as the tram passes over them. At any one time, no more than two consecutive segments under the tram should actually be live.
Read more about this topic: Ground-level Power Supply
Famous quotes containing the word technology:
“The real accomplishment of modern science and technology consists in taking ordinary men, informing them narrowly and deeply and then, through appropriate organization, arranging to have their knowledge combined with that of other specialized but equally ordinary men. This dispenses with the need for genius. The resulting performance, though less inspiring, is far more predictable.”
—John Kenneth Galbraith (b. 1908)
“If the technology cannot shoulder the entire burden of strategic change, it nevertheless can set into motion a series of dynamics that present an important challenge to imperative control and the industrial division of labor. The more blurred the distinction between what workers know and what managers know, the more fragile and pointless any traditional relationships of domination and subordination between them will become.”
—Shoshana Zuboff (b. 1951)
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—Jackie Torrence (b. 1944)