Universal Security Instruments USI-1209 120-Volt AC/DC Wired-In Ionization Smoke and Fire Alarm

One of my several original units manufactured in Feb 2000, started acting up. The alarm would go off after several minutes and the light turned red rather than green with a freshly replaced battery. All of the other units appear to work properly: green lights with new batteries. I looked up the model of Feb 2000 original SS790 unit to see if I could replace it with the exact same model and learned that it had been replaced with this one. So I read a few review on this one and decided to give it a shot. It looks very much like the original, but the base was a little different. I first tried to simply reuse the old base, but could not get it to seat properly. I went into the garage and found the breaker for the detector, turned it off, and then replaced the old base with the new one. It was straight forward and intuitive. I simply used a screw driver to loosen the existing base to turn and remove it exposing three color coded wires. I disconnected the three electrical wires and connected the new base, tightening it down with the same screws. The new unit fit perfectly into the base. Once I turned back on the power, their was a green light. Holding down the test button, it sounded properly, and, no more alarm or intermittent chirping. If another one fails, I plan to replace it just like I did this one.

I ordered two new detectors exactly the same ones which went bad after 12 years. I didn't know it at the time but you are supposed to replace the detectors after 10 years or when they start making noise with no smoke around or anything else to make them go off. My original detectors were wired into my electrical system. . (I also changed the batteries every 3 years.)Since both detector are exactly the same, I simply removed the bad detector, and hooked up the wires into the new detector and everything worked just fine. I never touched the plate covering the hot wires or where the detector is connected to the hot wire. Very simple to do if they are similar. A new battery was part of the new detector. . .

I purchased this to replace a unit installed when my home was built in 2001.This USI unit had gone out (kept beeping intermittently) but I didn't want to put on a new base plate if I didn't have to do so. The Universal Security Instruments SS-790 fits right into the USI 1204 base plate. From reading the reviews it appears this SS-790 is a higher quality unit than the USI 1204. I have 7 wired units and am replacing them all with the SS-790.The unit does have a bright green light but we don't notice it - I know others have mentioned the green light is annoying.

We moved into a home that had an older version of these and one was missing but we didn't know where to get a replacement. Another one went bad so we decided to see if we could replace both units. Duh - enter Amazon. These fit perfectly and we are happy with them.

Hi,I broke the tabs that the base fastens the alarm to on one of my old ones, so I bought this replacement. It was easy to install. Just remember to turn off your breaker to your smoke alarms in your breaker box because I didn't at first and got a good jolt. Anyway If you are just replacing one of these there are three wires and you just connect them as the one that you took off. Anyway after I was done turned on the breaker and it worked. It comes with a 9v battery the base and alarm. Pretty good deal for a replacement.Kevin

When our home was remodeled in 2007, the contractor installed these alarms. They have never been a problem until last month when they starting alarming. Removed the units and installed new batteries but they still alarmed. Purchased replacement alarms and hoped the new units will attach to the already wired in base unit. They fit smoothly. One of your reviews commented that replacement alarms did not fit base plates. Well in my case, they attached without any problem.

Thrilled that I was able to find the 120v A/C detectors and as replacements for my 25 year-old existing one's they were a snap to install. Very much more sophisticated of course, plus battery back-up that my older units never had. A satisfied customer! Thank you.

Bought this to replace one in our house that went bad 'like for like'. Works, no muss, no fuss. It is not a dual sensor until however, and I can find no reviews as to its testes efficacy (i.e. consumer reports), but it is UL listed so in theory it has passed the stringent UL listing requirements for a smoke detector.