# How to attach two phone wires to make one

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

By blkhawk Follow

## 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

• 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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## 10 Comments

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. ðŸ˜‰ This is how most coaxial wires are, the center conductor is the positive/hot and the outer conductor/shield is the negative/ground.

Reply 6 years ago on Introduction

Reply 8 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.

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 9 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.

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

Reply 9 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.

Modern wireless telephone systems have largely eliminated the need to outfit your home with many phone jacks, since a central phone jack can now serve a single transmitter/message unit that sends signals to several wireless remote handsets that can be used anywhere in the house. And there are now many homes that have no land-line phones at all, relying instead on cell phones only. At one time, it was common for homes to have a phone jack in every room; today's homes may have none at all.

But if your home still has a landline, it's sometimes necessary to establish additional phone jacks that are hard-wired to the main telephone system. For example, in very large homes, wireless receivers may have trouble receiving the signals from a single transmitter. In these instances, the solution is often to run phone cables to remote locations and install jacks that can serve their own transmitters. It's also possible you may need to replace the main phone jack that serves the central cordless transmitter, should it wear out.

Fortunately, this increasingly rare DIY project is still quite an easy one to complete.

## Before You Begin

In older telephone installations, the phone cable typically has four small-gauge wires inside the outer jacket: red, green, black, and yellow. If you’re extending a line to a room or other part of the house, you can continue to use this type of cable, or you can use newer Category 3 or 5 (Cat-3 or Cat-5) data cable, which also has multiple wires but with a different color scheme. Cat-3 or Cat-5 cable works just as well as the old cable for phone service, and it works much better for data (such as for a DSL internet connection). With either type of cable, once the cable is run to the jack location, the wiring of the jack is a simple matter of matching up the correct wire colors.

Our project assumes the phone cable to the new jack location has already been installed. Running phone cable is generally any easy process, in which the wires at one end of the cable are first attached to the matching screw terminals on the main phone terminal block. After the cable is run through the walls or under the floor to the new location, finishing the job is usually just a matter of hooking up the wires to a new jack using the same color-coding. Running phone cable through finished walls uses many of the same techniques that are used for running electrical circuit cable, but the job is considerably easier since phone cable is quite small and flexible.

## Safety Considerations

Telephone wires inside your home carry a very low-voltage electrical current and are generally quite safe to work on without shutting off the power. In fact, only the phone company can shut off the power to the phone system. But just to be safe, don’t work on phone wiring with wet hands or when standing in water.

Two-line phone options are seemingly limitless. Retailers advertise a plethora of phones with multiline capabilities. There are two-line business phones, two-line touch phones and two-line cordless phones. Two-line cell phones are even an option now.

All telephones have a jack where you plug in the phone cord. The phone jack is connected to the wall jack, which connects to the telephone company’s wiring. The phone jack is lined with contacts, or conductors, that recognize the wires inside the cord and establish a connection with the line. Whereas the contacts in a two-line phone jack automatically recognize all four wires, and thus both phone lines, the contacts in a single-line phone jack only recognize the first line. So even if you have two phone lines up and running, if you plug the two-line cord into a single-line phone jack, you’ll still only receive calls from the first line.

Two-line phones instantly recognize both phone lines and detect which one is ringing. It’s possible to use two phone lines without using a two line phone, but you have to either rewire your wall jacks or purchase a two-line splitter. These devices plug into a standard two-line jack and split the line, directing the first line to one jack and the second line to the other jack. With a splitter, you’ll just have two single-line phones coming off the same jack. One of the phones will receive calls from line one, and the other will receive calls from line two.

Ultimately, two line phones aren’t that different from their single-line counterparts. Take a look inside these double-duty devices on the next page.

Many cell phone carriers now offer second-line service on individual handsets. With this feature, you can add a second phone line with a different phone number to your existing phone. All you have to do is sign up for a second service plan. With two lines on the same phone, you can designate distinct ring tones, subscribe to different services and get phone numbers with different area codes. Two-line cell phones are perfect for people who want to keep work and personal calls separate.

Through our some recent articles we published a review of Samsung A50s and discussed about USB Type C. Samsung A50s is kind of starting range of Samsung premium devices – you’ll get more options after connecting two Note 10 (both devices support pen and touch with palm rejection). Commonly, most of the entry grade to mid-range smartphones have micro USB, not USB Type C connector. USB OTG works in the same way for micro USB and USB Type C. We tested the system by connecting :

1. Samsung A50s with Vivo Y71
2. Samsung Note 10 with Samsung Note 10+

We are writing from the experience of connecting Samsung A50s with Vivo Y71. We believe that this kind of combination is common. Vivo Y71 has an option to turn ON/OFF the OTG. We kept the OTG of Vivo Y71 to off. Samsung A50s acted quite like a computer.

The smartphone charger cable supports data transfer. So :

1. You can use one smartphone’s charger cable and a connector for converting the standard male USB end to micro USB or USB Type C convertor
2. or, you can use charge cables of both smartphones, in that case, you need to connect the two male USB ends – a connector with both side female required
3. Obviously, you can buy a dedicated cable with the desired ends

Whenever you’ll connect holes of both the smartphones (male-female connectors are not sober langugage either) :

1. One will work as a master, one will work as a host. You’ll get onscreen option to control which smartphone you’ll use as the master.
2. The smartphone with lesser battery charge in percentage will suck battery from the other to get charged.

There were some protocols standardized for digital cameras before the advent of these smartphones. There is
Media Transfer Protocol (MTP), Picture Transfer Protocol (PTP) and so on. There are many benefits of MTP, such as
driverless installation, Auto Sync, auto-guess device limitations, bidirectional file property synchronization and so on. By default, Samsung’s compiled Android extensively supports sync between two smartphones in this way. You need just a few taps to guess how the file manager can “suck” files from the other device. You can select, copy, paste from the Samsung device as you do on a computer.

There is a difference of Media Transfer Protocol (MTP) browser with USB Mass Storage (file oriented instead of the block-oriented protocol). MTP avoids exposing the filesystem and metadata index. There is no risk of filesystem corruption if unplugging the device while writing. Also, file transfers are atomic, and no unmounting is required.

Samsung assumes that both connected Samsung smartphones belong to either the same person or the same family. You can easily sync the Gallery of two Samsung smartphones. Samsung has an app to share the battery with another device.

Do not try this with a costly DSLT/DSLR. Their standard does not allow unauthorized writes.

#### About Abhishek Ghosh

Abhishek Ghosh is a Businessman, Surgeon, Author and Blogger. You can keep touch with him on Twitter – @AbhishekCTRL.

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## Introduction: Simple Intercom From a Pair of Old Corded Phones

By DIY Hacks and How Tos DIY Hacks & How Tos on YouTube Follow

An intercom can be a useful tool or a fun toy. In this project, I am going to show you how to make a simple intercom using a pair of old corded telephones. This is an easy electronics project that is great for beginners and fun to do with children.

## Step 1: Materials

Materials
Two Corded Telephones
Phone Cord
9 Volt Battery
300 ohm Resistor (270 ohm or 330 ohm can also work)
Heat Shrink Tubing
9 Volt Battery Connector
Small Plastic Project Housing

Tools
Wire Strippers
A Sharp Knife
Soldering Iron
Screw Driver

## Step 2: How the Intercom Circuit Works

At its most basic level, a telephone network is just two microphones, two speakers and a power source. In this project we are reducing the phone to these basic elements. The handset of the phone contains the speaker, the microphone and any necessary processing circuitry. All we need to add is the power source.

A regular corded telephone doesn’t require much electricity to operate. It just needs about 9 volts and less than 30mA. It normally gets this from the phone line itself. This is why many phones can still work even during a blackout. However in this project, we are using a single 9 volt battery to power our phones.

The battery is wired in series with a 300 ohm resistor and connected to either the red wire or the green wire in a phone cord. The phone cord is then plugged into both phones. The battery is able to supply enough electricity to power the speaker and microphone circuits of both phones. This allows you to use them to talk back and forth.

## Step 3: Separate the Internal Wires of the Phone Cord

Inside most phone cords there is a red wire and a green wire. If your cord has four wires (red, green, black and yellow), you only need to pay attention to the red and green wires. We need to connect our battery and resistor to either the red or the green wire. Because we only need to connect to one of the wires, the other wire can be left untouched.

To access the wire, I used a sharp knife to cut down the center of the cord for several inches. Then I cut off the insulation from one side to reveal the red wire. I cut the red wire at the middle and stripped the insulation off of the wire at each cut end. This is where we will connect the battery and the resistor.

## Step 4: Connect All the Components to Test It.

It is always a good idea to test a circuit before soldering it together. To do this we need to connect all the components. You can do this with alligator clips, plain jumper wires, or you can just twist the ends of the wires together.

Connect one terminal of the battery to one of the red wires and connect the other terminal of the battery to the resistor. Then connect the free end of the resistor to the other red wire. Plug the phone cord into both phones and you are ready to test it.

Speak into one of the phones and have someone listening to the other. This works best if they are in a different room. You should also be able to hear them speaking. If their voice is too faint, then you should try using a smaller value of resistor.

## Step 5: Solder the Battery Connector and the Resistor to the Phone Cord

If everything is working, then it’s time to solder everything together. I highly recommend insulating each connection with heat shrink tubing. If you decide to do this, you need to slide the heat shrink tubing onto one of the two wires before soldering them together. Then after you are done soldering, slide the tubing over the exposed wires. Now heat the tubing with your soldering iron or a lighter to shrink the tubing so that it is tight around the wires. Do this for each connection.

## Step 6: Mount the Parts in a Plastic Project Housing

No project is complete without a housing to keep all the parts neatly together. I used a 3″ x 2″ x 1″ plastic project enclosure from RadioShack. We only need to make one modification to it. You need to cut a hole in each side for the phone cord. To do this I held the cord up to the side of the housing at the opening and marked the outline of the cord. Then I cut out the marked area with a sharp knife. Do this on both ends of the top and bottom piece of the enclosure.

Now just carefully fit all the parts into the housing and close it up. Plug the phone cord into both phones and your intercom is done.

## Step 7: Using the Intercom

When you speak into one phone the person at the other phone should hear you clearly. Now you just need to run a phone cord between the two locations where you want the intercom to be located. To turn the intercom off, simple hang up one of the phones.

The only problem with this design is that there is no way to make the phones ring. One potential way to deal with this is to use a phone cord with four wires in it such as a “4 conductor line cord” and use the two extra wires to set up some kind of buzzer or LED indicator.

## Step 8: Optional: Power the Intercom With an AC Power Adapter Instead of Batteries

With a typical 9 volt battery, you should get 20-30 hours of use out of the intercom. Keep in mind that the phones still use a small amount of electricity even when they are hung up. So the battery will not last forever.

If you would like to make this project a more permanent intercom system, you can replace the battery with an AC power adapter. I did a whole other project on how to replace batteries with an AC power adapter using a simple voltage regulator circuit. You can check it out here: https://www.instructables.com/id/Convert-Battery-Powered-Electronics-to-Run-on-AC/

If you try this method, I recommend setting the voltage regulator to 6 volts initially. Then gradually increase the voltage until you reach the appropriate volume in each receiver. Do not exceed 12 volts. If you go beyond this, there is a chance that you might damage the circuits.

There are three standard ways of wiring a phone jack. T568A, T568B and USOC. The difference is what colors are connected to what pins on the jack.

## RJ45 4-line to 2 RJ11 2-Line Adapter

There are a number of different splitters (usually named 400E) like this Suttle 400E Cat5 Splitter that plug into the RJ45 Jack and have 2 RJ11 jacks each with 2 lines. These are fairly easy to find but just make sure youre not getting a regular telephone splitter (1 RJ11 to 2 RJ11). It needs to have a male RJ45 on one side and 2 female RJ11s on the other.

## Break Out Box

Manufacturers of structured wiring systems also have premade break out boxes that will allow you to access the 4 lines in different ways. The Leviton 47609-4×4 4×4 Breakout Module is one example.

## DIY RJ45 to RJ11 Break Out Box

If you cant find the break out box above or have special needs you can make your own break out box.

You can make one anyway youd like but to give you an example lets make a a 4 port box that takes an incoming cable and splits it up to L1&2, L2&1, L3&4, L4&3 similar to the Leviton.

• A 4-port surface mount keystone box (C&E Blank Surface Mount Box for Keystones, 4 Hole, White (CNE43705))
• 4 Phone jack keystone ports (like these ONQ / Legrand F9042WHV5 RJ25 Phone Jack, White, 5Pack)
• 1 RJ45 Connector.
• Punch down tool with 110 cutting and non cutting blade
• Modular Plug crimper
• Screwdriver

Were going to daisy chain 2 pairs on 2 ports for Lines 1 & 2 and then do the same on 2 other ports for lines 3 &4 so well have 4 jacks wired like this:

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By Dave Rongey
Summary: This telephone wiring diagram with photos and instructions will show you the direct steps to correctly wiring a telephone jack.

## Electrical Wiring and Repairs Made Simple

Wiring a Telephone Jack
After installing the Cat 3 – 3 pair phone wire I am ready to install the wall jack. You will have a wide variety of telephone jacks to choose from but the wiring for a single line phone service will be standard.

Keep in mind that the colors of the telephone wiring in your home will be typically one of two types or insulation colors. Older telephone wiring was a basic Cat-3, 4 conductor or 2-pairs with red, green, black, yellow.

Newer homes can have anything from Cat-3, 3-pair on up to Cat-5e, with 4-pairs, with the insulation colors being a combination of solid and solid with white for each wiring pair. The wire pair colors are blue, orange, green and brown.

## This Wiring Diagram shows the standard way to Wire Telephone Jacks

 The single line set will use the following pairs depending on your cable: Red Wire – Green Wire White Blue Wire – Blue/White Wire Quick Fix Tip: After you connect the wire pair to the jack and you get a Dial Tone but you do not hear tones when you dial a number from a button pad then just reverse the pair.

## Recent Questions and Comments

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## Basic Home Electrical Wiring by Example

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### Home Electrical Wiring

All home electrical wiring projects should be performed correctly by trained and qualified individuals who understand the principles of electrical circuit wiring and the basic fundamentals of home construction.
Detailed information is provided throughout areas of this website about the complexity of specific projects to help assist with you to understand the scope of work involved.
The following categories will provide more specific information for each project – below is an Example:

Electrical Project Skill Level:
Intermediate to Advanced – Best performed by a Licensed Electrical Contractor.

Electrical Tools Required:
Basic Electricians Pouch Hand Tools and a Voltage Tester.

Estimated Time:
Depends on the personal level experience, ability to work with tools, install electrical circuit wiring, and the available access to the project area.

Electrical Safety:
Identify the electrical circuits found in the project area, turn them OFF and Tag them with a Note before working with the electrical wiring.

Home Electrical Parts and Materials:
Electrical parts and materials should be approved for the specific project and compliant with local and national electrical codes.

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