It was common practice when the single decker Interurbans were introduced to lower the pantogrphs when the train was stabled. This meant the cleaners had to use the on board batteries to power up the lights at night.
It was soon found this flattened the batteries very quickly and with no battery power, the pantographs could not be raised forcing the driver to use the Hand air pump to raise them so they installed external power receptacles to enable the lights to be run of a power source and not the internal batteries.
When the double deckers were introduced, they too were to be stowed with the pantographs down but this apparently caused problems with the A/C units so they had to be left raised.
In the overhead electrified areas, to enable the rails to carry the return current of the trains and the signal voltages, a devise called an Impedance Bond was installed between the rails near a block joint. Today these are now located beside the running lines partly to allow track maintenance to be carried out without damaging them as well as not being damaged as before with a derailment.
The inside of these Impedance Bonds, nicknamed 'Turtles' because of their shape is filled with a thick copper bar wound in a coil.
The principle being it will allow the 1500 Volt DC to be passed from section to section but block or 'impede' that voltage going through to the signal relays.
During a 'Closedown' between Mt Victoria and Blackheath someone made a mistake and when the first Train entered the section, all the power was routed through the signal hut and basically blew the guts out of everything inside.
All the cables had melted and all the relays were a blackened melted mass of carbon.
The Hut itself survived although it blew out the fibro sheets on each end above the doors.