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

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## 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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• ### 3D CAM and CNC Class

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## Questions

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!

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.

2 replies

resistor value

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?