If anyone knows about the type of wiring used back in the day in NYC when it runs through piping in buildings PLEASE HELP!!!!!!!!!! I'm changing a simple light fixture and coming out of the ceiling connecting to the old fixture is three wires with there ends twisted together into one and a fourth wire by its self. the old fixture had a brown wire connected to the 3 wire group and a blue wire connected to the single ceiling wire. no black, white, or green. how do I find my neutral wire and my ground. and whats the difference between the two? any and all info needed. thanks

Old "conduit"

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