How to Connect Two Phones at Home for an Intercom or for Children Amusement




Introduction: How to Connect Two Phones at Home for an Intercom or for Children Amusement

I was inspired by two Instructables to create an intercom at home.
The only difference in mine was using a dead laptop power supply to power the telephones instead of batteries. Like it is appreciated in the picture I drilled a hole on a plastic electrical box and pushed the wire through. I made a knot to avoid someone yanking the wires of the phone jack by accident.

Step 1: Using Solderless Connectors

The 20 volt transformer came with just one white colored wire and another braided wire around this single wire. I assumed that the white wire was the "live" or negative charged wire and the braided uninsulated wire was the "neutral" or positive wire. I was pleased to discovered that I was correct.

Step 2: Connecting the Wires to the Wall Jack

With a crimper I connected all the wires.
  • Live or negative (the red wire on the picture) to A jack green
  • Neutral or positive (the black and red wire) to B jack red
  • Connect a resistor between A red and B green

Step 3: Enclosing the Project

After I connected all the wires I enclosed the project. Soon my children were talking to each other using this "intercom".

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    Thanks for giving me credit for the "Old Phone Intercom Device", its much appreciated. I like your use of an AC adapter to avoid the batteries. Great Instructable!

    J,R,D, Ltd
    J,R,D, Ltd

    7 years ago on Introduction

    The "live" wire would be positive (+) not negative and the "neutral" would be negative (-), just thought I'd point that out for ya. ;) This is how most coaxial wires are, the center conductor is the positive/hot and the outer conductor/shield is the negative/ground.


    Reply 7 years ago on Introduction

    The word that I should have used is cathode which most times is negative. In a DC circuit electrons flow from the negative (cathode) to the positive (anode). The convention is to say that a positive charge "flows" to the negative side and all mathematical calculations work either way.

    I love this!

    When I was a child, I had an old worn out corded telephone. To make it more fun, I connected a 9v battery to the phone, and had tones. I've been hooked on comm since.

    Have been wanting to do a project that could act as a very simple field telephone. Something that could be easily used and deployed within communities in an emergency. Possible phone points may be: headquarters, first aid station, cooking area, etc.

    A makeshift switchboard could probably be constructed pretty easily in order to connect multiple handsets. If the two jacks are simply connected in series, I see no real reason why more jacks wouldn't also work. Having multiple handsets in use at one time may cause disruption, though.

    Could this idea work at, say, 12v?

    Thank you for your ideas!


    Reply 8 years ago on Introduction

    It is my understanding that the more voltage (battery or wall wart) used is somewhat directly proportional to the length of your wires. I selected a 20 volt wall wart since the wires connected two rooms and it required 30 feet or more of wire.


    8 years ago on Introduction

    Nice ,
    How can i have more then 2 phones :) , with ability to dial to each other. sorry for being noob


    Reply 8 years ago on Introduction

    There is another Instructable that explains how to build an intercom with buzzers to let anyone know when to pick up the phone. To hook up more than two phones you will need some sort of switchboard and that is beyond my abilities at this point.