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At 3:30 am a couple days ago, the smoke detectors went off. Not the 'low battery' noise, but full alarm triggering the others to sound off as well. I checked around, and with no actual issue, pulled them all off. 6:00 visit to Home Depot. Turned off the breaker, took my meter to verify dead wires, and started replacing them, 6 total. The alarms came with wiring adaptors which were mostly fine. In 2 cases, there was already such a rat nest of wiring that I had to just use the actual wire and skip the adaptor to save space.

In this box, there was more than just connectors. And my question. Can anyone identify this? I have 3 floors, basement/first/second, and this was in the box on the first floor with a 4th connector. Other boxes had a lot of wire, but it looked pretty standard, in/out, and alarm. (And yes, crappy installation, that box is loose, but tight after putting mounting plate on.)

  • 1
    Any writing or identifying marks on that object?
    – Gunner
    Commented Dec 23, 2019 at 14:19
  • What do you mean by adaptors? Do you mean disconnect plugs? Check Code but I think you're not allowed to remove those... If your box is overfull get a box extension... Commented Dec 23, 2019 at 14:20
  • Also, that tape outside the wirenuts has to go. Anytime you see that, remove the tape and do a pull test. If it fails the pull test, redo the nut properly. Usually tape means it won't survive a pull test, and that means an poor, arc-faulting connection! Tape prior to wirenutting isn't all bad, but makes a pull test impossible, so may hide problems. Commented Dec 23, 2019 at 14:23
  • @Gunner - no. Both sides were black, as seen. Commented Dec 23, 2019 at 14:45
  • 1
    What was the brand of the original detectors?
    – Gunner
    Commented Dec 23, 2019 at 18:50

1 Answer 1


I'm going to go with... It's a smoke/heat/CO alarm relay. There are many different types and they all look different. This is quote from the Kiddie website "This module is only activated by a smoke alarm interconnect signal. The relay portion of this module can be used to activate auxiliary warning devices such as external bells and sirens, hallway or stairwell lighting. It provides isolated, (no internal connection to 120 volts AC) normally open, and normally closed contacts"

  • This doesn't seem to have enough wires connected to it to be a relay module (such as a SM120X) Commented Dec 23, 2019 at 17:19
  • It could be an old /discontinued /builders special / no name relay. Just used kidde a an example. There are 3 wires just like interconnected smokes. Black and white for power, and in this case yellow a the traveler would be all you need to notify something that the alarm is going off.
    – Gunner
    Commented Dec 23, 2019 at 18:41

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