When we bought this house in Seattle, Washington, the downstairs bathroom was framed, but unfinished. There is a thin gray cable hanging from the ceiling, and I can't identify it. Any guesses as to what this is?

The house is wired for security. Is it possibly connected to the security system?

Thanks! enter image description here


If there was a black wire in there, I would say it was a telephone line. The fact that the crimps are on red and green supports that theory, as red/green are the first to be used. (black/yellow were spares; they got a variety of uses such as Princess phone backlights, second phone lines and the like.)

It's also conceivable that it's doorbell or thermostat cable, or phone cable re-tasked for those purposes. (phone wire is a little light for that).

It's definitely not AC power.

  • Seems reasonable. The fact that it was over a bathroom is probably a red herring. It's probably an abandoned line. – isherwood Jul 10 '17 at 16:35
  • I would suggest cutting back the jacket on the wire some to see if there is actually a 4th black wire in the cable. If so then I would also agree that there is very strong evidence that this is a land line telephone wire. Also it is most likely that such wire has solid copper conductors albeit that they are very small in diameter. – Michael Karas Jul 10 '17 at 16:51
  • It's telephone cable. Originally ring voltage was carried on a 3rd wire. – Tyson Jul 10 '17 at 21:39
  • The house was wired for security and many installers in years past used this type of wire because the systems were 12v most of the time. Each device required 2 wires for the power and 1 for the signal back to the controller on the motion detectors. systems also monitored the power on each channel to watch for the sensor being bypassed for the window and door open switches only 2 wires needed for each switch. – Ed Beal Sep 14 '17 at 19:20

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.