Turntable bridge question

[Blind Bruce]

What is the purpose of the "hoop" that goes from one side of a modern turntable bridge to the other?

[ARTHILL]

Among other things it carries electric wires from the power plant to the turntable.

[selector]

Bruce, below the tiny operator's shack is a housing.  That would have carried either a pneumatic motor or an electric one, depending on the type of mechanism.  Either way, a hose or cable was needed to run a compressor, provide compressed air via lines, or provide power to a motor that was wither a direct drive or the compressor motor.  The way to do that was similar to what happens when a man holds his hand high and allows his dancing partner to pirouette below it.  The harp or arch supports the cable running from a nearby pole to the harp's receiver device, with the cable being like the lead dancer's arm held high.