How to Install an Intercom System

Although wireless intercom systems are easier to install, if you are building your home a wired intercom system still has many advantages.

Getting Started

For example, if you are building your home in a new development, other structures -- such as homes and businesses -- may be built near your home in the future, and could contain wireless or radio devices that might interfere with your wireless intercom system. You would then have to go back and re-install a wired intercom system anyway, at a much higher cost than if you had put the system in during the building process. .

Most intercom systems come with a main interface panel and at least four smaller "call panels" that are used in different parts of the house. The first step is to determine where you want to put the main panel. They are typically placed in a room where the residents will spend a lot of time, such as a family room or kitchen. The main panel should also go above an electrical outlet so it can easily be plugged in. it is also a good idea to place the main panel on a wall that can easily be accessed through the attic. Wires will need to go up behind the wall and through the attic.

Decide where the smaller panels will go. Most homeowners will place a smaller panel in each bedroom. Basements are also popular. Keep in mind that many intercom systems allow you to set up your telephone system to answer calls at the front door, or make calls to the different panels around the room. So even if you can't put a call panel in every room, if you have a cordless phone system you can still use the intercom system from any part of your home.

Use the pencil and the measuring tape to draw a box on the interior wall where you will place the call boxes. Cut holes with drywall knife.

Replacing the Door Strike

Unscrew door strike. Pull device out of outside wall and look at the wiring. One set of wires will go to the doorbell ringer inside of the home. Another set of wires will go to the door strike transformer, which provides power to the door strike. Cut the wires connecting the door strike to the doorbell ringer.

Position the stepladder below the space in the ceiling where you will make your mark. Use the pencil to make a dot in the ceiling where you will drill. Put the ¾ inch bit into the drill and drill a hole in the ceiling. Bend the top wire of the coat hanger slightly and feed it through the hole. Push the coat hanger up into the attic until it stays in place.

Enter attic. Bring the power drill, ¾ inch drill bit, electrical wire and fish tape. Find the top of the coat hanger sticking up through the attic. Determine where the door is in relation to the coat hanger. Drill approximately three inches away from coat hanger. Your hole should now be between the interior and exterior walls. The interior wall will be drywall or similar material and the exterior wall will be brick, wood, etc.

Take the end of your wiring cable and attach it to the fishing tape. Feed the fishing tape and wire through the hole in between the two walls until you reach the door strike. Leave the wire spool and fishing tape in the attic. Exit the attic and go back to outside of the front door. You should see the wires attached to the fishing tape. Remove the wire from the fishing tape. Connect the wire that was on the fishing tape to the old wires that are attached to the door strike. Braid the two wires together and cover with a red wire cap. Feed wires back through opening and push door strike back into place. Screw strike panel until it is firmly attached to wall.

Go back into the attic and attach another spool of wire cable to the fishing tape. Feed the wire through the same hole as before, until you reach the part of your interior wall where the door strike transformer is located.

Unscrew the door strike transformer and inspect the wiring. You should see the wires connecting the transformer and the door strike. Leave those alone. Connect the wire you fed from the attic to the door transformer, then put the transformer back into place.

Installing the Intercom Panels

Inside the home, go to the spot where you want to install the main intercom panel. Look up at the ceiling, and find a spot to mark with the coat hanger. Take the stepladder and mark the ceiling, then drill a hole and put a coat hanger through the ceiling to mark your place. Repeat this process for each additional intercom panel you want to install.

Take the drill back into the attic. Find the wires from the door strike, which should still be attached to the new wire spool. Run the wire across the attic until you find the coat hanger near the main intercom interface. Drill a hole about three inches closer to the outside of the house from the coat hanger. Make this hole larger than the size of the bit, because you will feed wires from the door chime, the door strike, and the additional intercom units all through this hole. Unspool enough wire so it will reach the main intercom interface, then unspool an inch or two more so you can work with the wires easily. Cut the wire from the spool. Attach the end of the wire to the fishing tape and feed it through the hole. Keep feeding wire until you have reached the main intercom interface area. Feed the wire from the door strike transformer down the same hole.

Exit the attic and go to the main intercom interface panel. Behind the panel will be a main controlling board, where you will connect the wires from the door strike, the door strike transformer, the door chime and the other intercom stations. You should see the wire from the door strike attached to the fishing tape. Detach the wire from the fishing tape and connect it to the position indicated on the main controller board. There should be a slot clearly identified on the controller board that says "Door Strike." Connect the wire from the door strike transformer in the same manner. There should be a slot clearly labeled "Door Strike Transformer."

Go back into the attic and feed wire from the spool to each additional intercom station. Run out the wire spool from each location to the main interface unit. Feed these wires through the same hole you fed the wires for the door strike and the door strike transformer. Connect new wires to the door bell ringer and feed this wire down the same hole above the main interface area.

Connect the wires at each additional intercom station. Then connect the wires to the main intercom interface. Plug in the main intercom interface to a wall outlet. Test the system to ensure that communication is possible between all stations. Test the doorbell to ensure the reception is possible between the door phone and all interior stations.

Final steps

Test the doorbell to ensure the reception is possible between the door phone and all interior stations.

Use spackle and the putty knife to patch holes in ceiling.

Remove all tools from the attic.

Things You Will Need

  • Power drill, preferably cordless
  • Three-quarter inch drill bit for interior walls
  • Fish tape
  • Drywall saw
  • Coat hanger
  • Wire stripping tool
  • One-quarter inch screw anchor (x2)
  • Measuring tape
  • Pencil
  • Phillips head screwdriver
  • Wire cutters
  • Wire spool (x2)
  • Coat hanger (x6)
  • Drill bit (4 1/2-inch size)
  • Spackle
  • Putty knife
  • Red wire cap
  • Stepladder


  • This job is much easier if you have someone else to help. Your partner can help pull wires down from the attic and steady the ladder while you are drilling holes in the ceiling. He or she can also help test the various intercom stations.


  • Make sure the power is off before you start cutting wires. Only reconnect the power when it is time to test the intercom stations and the door strike.


About the Author

Burke Moeller is the Writing Center Coordinator at the University of Mary Washington College of Graduate and Professional Studies in Fredericksburg, Virginia. He assists graduate students with their academic papers. He also has more than ten years of experience as a professional journalist, working as a writer, producer, reporter and editor for several news organizations, including Reuters television and NBC Washington.