Security & Fire Protection Systems/Smoke Alarm


I have an A.C. powered ionization smoke alarm, Mod#201 from Southwestern Labs in Costa Mesa, CA which apparently is out of business.  It started acting up in the middle of the night. I removed unit and disconnected the plug and took a look at it today.  It has no batter backup.  I'm sure it is the original installed when the house was built in 1985.  There is another in the basement that was installed in 1998 when we remodeled.  Not sure of the make on this but it does have a batter backup and is not connected to the other one as far as a I can tell.  If I purchasea new one, will I be able to plug it directly into the old wiring or will I need to contact an electrician?  Also, what make a model would you suggest.

Thanking you in advance.

The way to tell if they're "interconnected" to each other is by examining the wiring harness.  You'll see three wires coming from it.  Black, white, and yellow (some have red or orange).  If the yellow (red or orange) wire is connected, then you they're definitely interconnected.  If you replace one unit, you'll have to replace both (as the other won't be compatible with the new detector).  

I would recommend using a Kidde branded detector.  If you have gas burning appliances in your home, I'd switch them BOTH out to a unit that's a combination CO and photo-electric smoke detector.  I believe the model number is KN-COPE-IC (  There is a new series of detectors that Kidde has released with a non-replaceable battery with a ten year life.  I wouldn't suggest using this one if your area has a large number of power failures.  Once it starts beeping "low battery" you have to replace the whole unit.  You can pick up the detectors at Lowe's, Home Depot, or Walmart.

You'll likely won't need an electrician to replace the wiring harness on your smoke alarm.  Put the old unit back in, and have someone run through the individual circuit breakers to find the one that turns the power off to the unit (the power LED will turn off).  Leave that breaker switched off, take down the old detector, and remove the base.  Remove the wire nuts one at time from the old harness and hook up the new harness to the same wire (black to black, white to white).  Stuff the wiring back into the box, and install the new detector's base assembly.  Plug the new unit back in and "voila", Bob's your uncle.  The new detector will come with detailed installation instructions that will likely illustrate what I've just written.  :-)  

If you have a problem, or need additional help, please don't hesitate to call 1 888 340 3473.  We're here 24/7.

Test your smoke alarm regularly.  Stay safe!

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Frank Kurz


Questions relating to Burglar Alarm and Security Equipment, Fire Alarm and Extinguishment Systems, Access Control, CCTV Systems, Installation, Service, Testing, Verification


30 years installing, servicing, and testing security, access control, extinguishment, and fire alarm systems

Chair of ULC Working Groups for Fire Alarm Testing (CAN/ULC-S536) and Fire Alarm Verification (CAN/ULC-S537), Executive Director of the Fire Protection Technicians Network (

Publications, Better Business Bureau Magazine, Applied Science Technologists and Technicians of British Columbia ( SUPPRESS! and Techs Fire Break Newsletters

Associate in Science; Emergency Systems (University of British Columbia); Aircraft Maintenance Technology (BCIT)

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