How to Create Your Own Home Intercom System

a corded phone mounted to the wall
  • 2 hours
  • Intermediate
  • 25
What You'll Need
In-line coupler
9 volt battery connector
9 volt battery
Wire cutter
Wire stripper
Dremel tool
Soldering gun
300 OHM resistor
Electrical tape
2 telephones
2 CAT 1 cables (telephone cords)
Ring-tone generator

Shouting around the house to find a loved one can get tedious and frustrating. You can solve that problem with a home intercom system. There are plenty of home intercom systems that you can purchase, but costs can add up quickly. Instead, use those old telephones laying around to build your own home intercom system. The article that follows will show you how to turn two old telephone units into a home intercom system. The process is rather simple and very inexpensive.

Step 1 - Expose the In-line Coupler

Open the telephone in-line coupler by applying pressure to the center of the plastic casing. With enough pressure, the coupler will snap open to expose the internal components. If you are having trouble opening it then you may try using a screwdriver with a flat head or using the side of a table or desk. Once the coupler is open there will be 4 colored wires: yellow, red, green, and black. The only wires in the coupler you need to worry about are the red and green wires. You can cut and remove the other two wires or leave them intact. They have no bearing on the home intercom system you are making. You can also complete this process by cutting into the wiring that goes to the telephones instead of going directly through the in-line coupler.

Step 2 - Set Up the Wires

The bread and butter of the home intercom system are the wires inside the in-line coupler. Snip the red wire as close to the center as you can so you will essentially have two red wires. Strip both ends of the cut red wire. Solder one of the red wires to the resistor and the other end of the resistor to the 9-volt battery connector. Now, solder the remaining end of the 9-volt battery connector to the other red wire. Remove any excess wire as this should be fully contained inside the plastic casing.

Step 3 - Test the Home Intercom System

With the soldering complete you can now test your new home intercom system. Plug a phone into each side of the coupler then install a 9-volt battery. Pick up the phones and start talking to test the system. You can use two cordless phones if you like but each phone will need to be fully charged in order to work. Once you are sure the home intercom system will work you can install the purchased ringtone generator. Follow the instructions for the generators as they are more complicated.

Step 4 - Finish Up

Wrap the exposed wires with a piece of electrical tape. Carve out a small notch on each side of the coupler where they snap together. Carefully close the coupler putting the wires for the 9-volt battery connector between the notches. You can use telephone cable as long as you need it to be in order for both telephones to be in separate areas.