Does the traction power to this section of overhead wire still have switching so that it is only energised (by use of track circuits) when a tram is actually approaching or traversing the section ?
Is the track on this section parallel to the airport runway ?
With regard to your query Noel, have sourced the following information:
ESSENDON AIRPORT - OVERHEAD ISOLATION
At the request of the Department of Civil Aviation it was decided in February 1954 to isolate the overhead in Matthews Ave. (poles 320-338) at all times except when a tram is in the section as the track crosses the approach path to the airport runway. Operation is triggered by isolated sections of the inner running rail on both up and down tracks about 70ft. Before the "dead" section of overhead. An underground cable continuously supplies power to the overhead beyond pole 338 and operation of the equipment is indicated by colour lights. As soon as the leading wheels of a car leave the insulated rail upon approaching, a relay is operated, closing the circuit breaker and energising the trolley wires. Two green lamps then light indicating the the driver is free to proceed. When running over the section of rail at the other end the wires are automatically de-energised. If more than one tram operates in the normally isolated section the wires remain energised until the last vehicle leaves the section. The system also operates on "band road" running. If the green light does not show when the tram runs over the approach rail the driver must operate a manual switch mounted in a box on pole 320. The overhead height in Matthews Ave. is lower than normal as an added safety measure.
Cheers, Wayne Duncan