Mystery 20/4 Conductor Cable on Pre-Install

I've pretty much wrapped up my Elk M1G install, but have a mystery cable which I have not been able to identify the use for. The person that installed it did not label it like the others. 3 door contacts were 20/2, 3 keypads were 20/4, a motion was 20/4, and an internal siren is another 20/2.

The cable is a 20/4, runs from the panel, all the way out to a wall stud plate drop, which goes into the wall where the cable/telephone utilities come in from. There is no cable exit on the outside of this wall, where the cable and phone lines exit the brick of the house and there are no blank plates on the inside of the wall that I see...the farthest point I can see is up in the attic where it drops down a hole in the wall plate next to the utility cable/phone wires.

I assume this was possibly to use for an external siren, but no idea why the wire wouldn't be brought out somewhere...

Anyone experience this?

Is there a telephone demarc box on this wall?  If so, any sign of the mystery cable there? 
 
I'm thinking this cable was meant to connect the alarm panel to the phone line.

There is, I opened the box but didn't see the said cable...only the incoming and phone cable going into the house.

But does sound like a logical use, I'd be surprised though, since all the phone lines in the house also run to the same central location as all the alarm wiring. Would have been just as easy to tap into the incoming and the house phone lines all right there at the alarm panel.

geogecko said:

There is, I opened the box but didn't see the said cable...only the incoming and phone cable going into the house. But does sound like a logical use, I'd be surprised though, since all the phone lines in the house also run to the same central location as all the alarm wiring. Would have been just as easy to tap into the incoming and the house phone lines all right there at the alarm panel.

Click to expand...

 
Your reasoning makes sense.  So if the mystery cable wasn't intended to connect to the phone line, I'm not sure what it would be for.  It might be for an exterior siren, as you suggested, but 20/4 is a bit light weight for that.  I would have expected 18 or 16 gauge. 

Hmm, guess I will have to do some more digging! Thanks for the suggestions.

You didn't mention if you used a tone/locator, my bet is this 20/4 went to the phone demarc but got pulled just inside. Either way, I'd hook up a tracer (I used to use the Progressive Electronics product -- was about $30, irreplaceable when I needed it) and see if it's at the phone place, an optional keypad or PIR left hidden. (I used to leave options hidden in the walls in the new-construction homes I did, with concise notes on where I could find it if the customer wanted to add the accessory)
Good luck.

Mystery solved! Almost never use my side garage door because there was stuff piled in front of it. Since this was a 4 conductor wire, I never thought it would be a door sensor. I opened the door a few days ago and discovered the prewired plug in place. Once I pulled the two conductors out enough to expose the jacket, I discovered the mysterious 4 conductor wire!

The other two wires were just clipped off, not sure why this was run instead of the two conductor stuff, but oh well.

Glad I bought a couple extra door sensors, because now this door is wired into the M1G.