Tram Controls - Pointswitching

Pointswitching

In some tramway systems points (switches) could be activated by the motorman from inside the tram, while the tram was still moving. In a commonly used and simple arrangement, the points would be operated by the motorman "cutting off" (i.e. returning the handle to the off position) or keeping power on while the tram passed beneath a special contactor in the overhead wires. The contactor would sense whether the tram was drawing electricity from the overhead. If the motorman cut off power the points were to be set for straight ahead. If the motorman kept the power on, the contactor sensed power was being drawn and the points would be set for the branch line. Because of their heavier demand on power, even when coasting, modern all-electric trams tend not to rely on this form of point switching.

In other more sophisticated systems the points are activated by a button on the driver's console, which sends a small electric ripple signal through the overhead to the points activator. Another system requires a transponder under the tram being recognised by a sensor which then sets the points for the appropriate track, depending on the route the tram is intending to take and which has been pre-programmed into the transponder.