Wiring – Any idea what these cables are for


We moved into a new house and I see these cables in our garage. They come from the ceiling and are right near our water heater and breaker panel. There are 2 cables. One cable is labeled “System to House” and the other is labeled “Back to Main”. One of the cable jackets says that it’s CAT-5e cable, but this doesn’t look like any Ethernet cable that I’ve ever seen, especially with those weird things on the end (LEDs, sensors?)

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Any idea what these are?

Best Answer

I can't quite be sure from the picture, but the red things are each joined to a wire from one of the two cables, right? If so, they're just splices, like wire nuts but for this kind of wiring.

So, this part doesn't tell us much about the purpose of the wiring. It could be any kind of signaling cable, though having the wires untwisted like that (and having only two connected, even) would not work for high-speed Ethernet.

It could be a telephone line (likely, except the labels seem a bit odd for that), part of a security system, or some kind of home automation. You will need to find the other ends of the cables to learn what they're used for.

If there are cables elsewhere that might be these but you aren't sure, you can get a "tone and probe" kit to send a signal on one of the unused wire pairs of one of the cables and wave the probe around other ends (or even through a wall) to detect where it runs.