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Recently bought a house that's about 40 years old. The previous owner was clearly very fond of doing the wiring himself and has left me some idiosyncrasies to work out. One is this box in one of my bedrooms. No idea what it is, or is supposed to do but I see extra wires coming straight out of the sheet rock on the bottom of it. Can anyone tell me what it is?generic DC adapter plugged into electrical socket.

Misanthrope Meanguy
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3 Answers3

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Conveniently, it still had the UPC barcode label and you captured it quite clearly in the picture.

A search at upcdatabase.com shows that it is:

Description     Brinks Home Security System AC Power Adaptor
Size/Weight     5x3x3, 12 ounces 
Issuing Country United States

A Google Search for that UPC brings up a number of hits, including on at Parts Express that shows the following specs:

Universal UB1640W 16.5 VAC 40 VA Plug-In Wall Transformer

AC Output Voltage   16.5 V
Current Capacity    2400 mA
Center/Tip Polarity AC Plug 
Input Voltage       110~120 VAC

generic DC adapter showing outlet prongs and wire connection screws.

So, it appears to be a low voltage 16.5 VAC transformer that is (or at least was) a part of a home security system. Looks like the screw on top is meant to screw into the outlet for semi-permanent installation.

Of course, it's possible that it was re-purposed for something else like low voltage lighting, a doorbell, or who knows what it may be used for.

Johnny
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    This. Simply put, it is a transformer to power an alarm system. – Speedy Petey Oct 22 '15 at 10:55
  • I always thought those output DC current – Kris Oct 22 '15 at 13:39
  • @Kris most power bricks are DC supplies, but they don't have to be. Old fashioned DC bricks worked by combining a transformer to make low voltage AC with a rectifier and capacitor to turn it into low voltage DC. Remove the 2nd half of the hardware and you've got an AC brick. – Dan Is Fiddling By Firelight Oct 22 '15 at 14:08
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    Well played, sir! – Doug McClean Oct 22 '15 at 14:36
  • Carefully screw it off and see if there's anything connected to those output terminals (perhaps being routed back into the wall?). A DIY genius might do something like that. :-D – KlaymenDK Oct 22 '15 at 14:42
  • They also had those (very similar) for Comcast Fios systems. – BrownRedHawk Oct 22 '15 at 15:05
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    I bought a house built in the 1990's (in the USA). It had a few of these that were put in place by a security alarm company. One powered the alarm control panel. The other powered a motion sensor up in one corner of a room. Seemed kinda hokey, but it was a system installed by a large, nationally known security company... – bitsmack Oct 22 '15 at 16:11
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    AC Step-down transformers. I've also seen many in commercial spaces running their door dingers/buzzers and old CCTV cameras. I haven't seen them running any modern CCTV equipment, but alarms still use them; they have DC inverters built into the board. Not sure why this is. But yeah, pro installers just run wires into a hole in the wall. Always seemed a bit janky to me. – user1103 Oct 22 '15 at 16:59
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    You can see a bit of drywall cut out (messily) at the bottom of the outlet - likely this indicates there is indeed some wiring going back in. – Joe Oct 22 '15 at 19:57
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    @Joe - also the poster's observation `I see extra wires coming straight out of the sheet rock on the bottom of it` also indicates wires coming through the sheetrock. – Johnny Oct 22 '15 at 20:48
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    Well, yes, if you read the entire post, but who does that? – Joe Oct 22 '15 at 20:49
  • The alarm system my brother-in-law had installed a few years ago has this, and it's AC output as well. I've been house-shopping recently and have spotted this in many of the houses I've looked at. The immediate giveaway that it's for an alarm system is that the wall wart is located on the same wall as the alarm control panel (though sometimes the panel is on the opposite side of the wall). – Doktor J Oct 23 '15 at 16:29
  • It's an inelegant "hack" to avoid having to call in (and pay) a licensed electrician to get power. Anything under 25 volts is "low voltage" and doesn't require an electrician to run in the walls. Obviously plugging something in an outlet doesn't require an electrician either. The "proper" (at least IMHO) way to do this is to wire the transformer into the outlet box. That would require opening up the wall (and closing up the hole again) versus fishing a wire through the wall, plugging in a transformer, and hoping the outlet cover hides any damage. – MacGuffin Dec 13 '21 at 00:37
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A transformer to reduce the house current to low voltage, to power something.

It can be for any number of things. If it goes into the wall, check the other side, there is a chance the wire comes straight through.

Jack
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This is a transformer or DC power supply. Odds are that this was installed years ago by the telephone company to power land-line telephones with light-up dials ("princess" phones). This was well before LED lighting that pulled small-enough power to run right off of the power from the central office.

DoxyLover
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