We all have old phones. Why not turn them into an intercom for your kids tree house. Or turn two old cordless phones into home base walkie talkie. Here is how.
Step 1: Materials
In-Line coupler (I got mine at Frys for 1.49)
9 volt connector (radio shack, or cut it out of some old piece of junk)
milk (helps keep you hydrated and keeps bones strong)
300 ohm resistor or close to it
black electrical tape
two telephone cords. (CAT 1 cable)
Step 2: Open Your Coupler
Apply pressure to break it open at the center, in the same way you might break a twig. You may press it up against the side of your desk if it helps. You will see 4 wires, they should be color coded red, green, yellow and black. If they are not, it will be harder. The red and green cables are the one you should worry about. The other two are for the second line; it will not affect this project at all.
Step 3: Cut, Strip and Solder
Cut the red wire in the middle. You now have two red wires. Strip the ends of both red wires. Now you will need some basic soldering skills for the rest of this project.
This sight has some good tips if your new:
Now solder one side of the resistor to one end of the red wire. Solder the other end of the resistor to one end of the 9 volt connector( it doesn t matter witch end). And the last side of the 9 volt connector will connect to the other red wire. It should look something like this. Now when you do this cut off exess wires from your resistor and 9 volt connector before you solder, remember it all has to fit back into the coupler when your done.
Note: int the photo I cut the yellow and black wires because they got in the way.
Note I also used 265 ohm resistor, because it was more handy. I have completed this project much earlier with out any resistor. Be careful if you do this, I am not sure what the implications are.
Step 4: Testing
Quick test, leave it open Plug two phones into both ends of the coupler put in the 9 volt battery and talk. You may use two old wall phones with no problems. If you use cordless you need to make sure you have power going to them before they will work.
If they work Seal the expose wire with black tape. Dremel out a little slit into one of the sides. This will be where the 9 volt connector wires will exit the coupler. Close up the coupler, and be careful not to break any of the soldering you did earlier. Bring the leads of the 9 volt connector out of that slit. See photo.
Step 5: Clean Up
If you use two cordless phones you have just made a makeshift home base walkie talkie. Clean up your area and drink your milk call a friend.
Note: to ring one of the phones you will need a ring generator, but that is another project for another time. Have fun.
Step 6: Troubleshooting
Make sure the cable works:
Find a phone where you can hear the dial tone. Now hang up and replace the line with the cable you plan to use, check to hear a dial tone now. If not then your cable is bad.
Make sure the phones work:
Temporary replace your home phone with one of the project phones, check to hear a dial tone. Then make a call to see if the microphone and the speaker work in the handset. And to see if the handset has a charge if it applicable. If you fail to make a call for any reason the phone is bad.
Make sure the Coupler makes a circuit:
Take the battery out of the coupler. The battery must be out. Then go to a working phone and make the connections in this order
Wall jack------> to cable -------->to the Coupler-------->to another cable------->to phone
This will check if you connected the right wires in the coupler. Pick up the phone and listen you should hear nothing, if you do here a dial tone then the wrong wires are soldered, or you have short in the coupler. If you move the coupler and you hear scratching sounds then you have a bad connection, and must re solder or better insolate.
If you hear nothing that is a good sign so far, now take a screwdriver or something metal and complete the circuit at the 9v battery connector. You should hear a dial tone now. If not then your connection on the red or green is just broken somewhere and you have to find it.
The green wire is just a straight shot; you do nothing with the green. The red wire is in series with the 300 ohm resistor and a 9v battery. Make sure its set up like this. I hpe this was helpful, drink your milk and have fun.