How Many Wires Are In Your Old NuTone or M&S Intercom System?

Home Intercoms

The old NuTone IMA-3303 home intercom system. The old NuTone IMA-3303 home intercom system.

Is your NuTone or M&S home intercom system old and out of date? Is it time to upgrade your system with a contemporary and stylish new home intercom, complete with modern features and the latest technology? The great news is that you don’t need to completely replace everything; you can still use the wires from your existing system. This means you don’t have to run new wires which saves you the need to call an electrician. A great money and time saver!

The first thing you need to do, even before you purchase a new system, is to determine what wiring system your current home intercom system uses. Why? Older systems use different types of wires, and the replacement models – also known as retrofit intercoms – are configured just as differently to work with each wire type.

There are four distinct wiring configurations: three-wire and four-wire are the most common, plus there is six-wire and the rare eight-wire. These wires are self-explanatory. A three-wire system, for examples, uses three wires. These wires connect your main intercom – also known as a master station – to the intercoms in each of your rooms – also known as room stations.

Again, you don’t need an electrician. You can easily determine the wiring system yourself in just four simple steps.

Older NuTone Room Stations
Samples of older-style NuTone Room Stations.

Four Simple Steps

Grab your screwdriver and head to one of the room stations – thats an intercom in one of your rooms. For this process, you can ignore your master station. The master is big and bulky with a lot of wires, and a room station is much easier to handle.

  1. At your room station, find the screws that hold the intercom to the wall. Each intercom is different, but it should be as easy as removing the screws from a wall plate. Remember to turn the screwdriver to the left – lefty loosey, righty tighty.
  2. Carefully pull out the intercom unit from the wall. Be gentle; you don’t want to pull the unit too far out that the wires rip off the back.
  3. Turn the entire intercom unit around just far enough so you can see where the wires are connected. Count the strands of wires connected to the intercom. If there are three wires, then you have a three-wire system. If there are four wires, then you have a four-wire system. And so on. (Connections vary from model to model; however, most intercoms connect their wires with a screw terminal.)
  4. Turn the intercom unit back around and reattach it to the wall with the same screws.

That’s it. You are done. Once you know what wire configuration your home intercom system uses, you are prepared to find a compatible replacement intercom.

There are a several choices that work well as replacements for old intercom systems, including NuTone, M&S Systems and the Intrasonic Technologies (IST) brands. To learn more about these retrofit options, read our blog entitled How to Replace Your Old NuTone or M&S Intercom System – or just give our friendly customer service department a call at 800-266-8765.

About Home Controls (410 Articles)
In business for more than 32 years, Home Controls is the premier national distributor for the most comprehensive and unique home automation systems.

8 Comments on How Many Wires Are In Your Old NuTone or M&S Intercom System?

  1. Hi, I would like to replace our 17 year old Nutone 4406. Is that a three or four wire system? Can I replace it with the IST Retro system?

  2. The NuTone 4406 is actually a six-wire system. And yes, you can replace it with the IST Retro System.

  3. I think I just need to replace the door speaker/bell(IS-67). I have a 3303 system(about 10 years old) that otherwise works well. The door bell is rusted, but nothing is heard if I connect the 2 wires that go to the bell to each other(i.e. bypass the bell). Additionally, when I measure the resistance across the speaker terminals, I’m reading an open circuit. Any thoughts??

  4. I have a 25 year old MS system.What can I replace it with and how difficult is it to install with basic wiring knowledge?

  5. Shannon Lebeuf // November 21, 2016 at 6:15 am // Reply

    I checked the wires on the back of my older M&S system, and there is a ribbon wire with 6 individual strands, but only split into 4 and connected to 4 screws, the end two screws attached to 2 wires. Is this a 6 wire system then?

    • Shannon:

      I’m sorry for the delay in response to your question, Shannon. Vacations and holidays.

      Bob Grier from our office will reply on Monday, as well as help you with any other questions you might have. He can be reached directly at, or by phone at 800-266-8765 x 107.

      Thank you, and Happy Thanksgiving holiday.

      Kayla Eide-Hall Marketing Operations Manager (858) 693-8887 x135

      [image: Home Controls]

      8525 Redwood Creek Lane San Diego, CA 92126

      [image: Blog] [image: Twitter] [image: Facebook] [image: Pinterest] [image: Google +]

  6. Great! Thank you so much for the article.

Leave a Reply

%d bloggers like this: