DIY Hacks & How To's: Phone Intercom

In this project, I show you how you can make a simple intercom system from a pair of old corded telephones. The phones already have all the circuitry that is needed for processing a voice call. All you need to add is a 9 volt battery and a resistor. This is an easy electronics project for beginners and it is great to do with children. Try it out and have fun.

[BrandonFrancey]

I did this years ago when I was in college. My buddies room was upstairs and mine was down stairs. When we did some LAN gaming it was a pain in the ass running up and down stairs getting things set up so I made this. What I did was I added a LED to the circuit on each end so when he picked up the phone, the LED would light up on my end and vice versa. What I found was that while I would always notice the LED and pick up, he rarely ever would notice. It was like he was studying or something. So I added a momentary push button on my end and a piezoelectric buzzer on his. I think I ran cat5 between the to jacks so I had extra pairs to work with but it all ran off of the 9 volt battery.

[persebra]

normally one would not need it these days with all the cell phones. but since its recycling something, and its just about free, this is a great idea. and a big finger to the NSA

[MrMattperreault]

Fantastic project! I'm going to try this with my students! Someone should post the instructions mentioned below for making it ring!

[jayfulf]

You can actually do this with cordless as well which allows you to have the bases very close together and the handsets wherever you want.

[lunhil]

I remember electricians doing wire runs had made battery powered handsets with alligator clips on them. They used the buildings wiring to communicate with each other through this system.

[grodenbarg]

done it. BTW: if you want to make a phone ring, you need to SAFELY pump about 90-120 volts AC through the line. LOL

[dinbee]

How do you make the other phone ring when calling that unit? Kinda missed it in the video. Some comments here said you gotta add 90-120v to it? How?

[MechInvent]

Dude you rock!! This was exactly what I was looking for.

[FNGFASHA]

Thanks for the video. Question. If I follow you video and put one phone in my house and the other in my shop, how can I make the one in the shop ring when my wife wants to talk to me from the one in house?

[shazizz]

Cool idea, now you need a ringer so the person at the other in knows to pick up the phone! Like an obnoxiously loud air horn!

[richkawaiipikachu]

Neat project, just would be nicer if theres a way to make the phones ring ethar via a.) picking up the handset to make the other end ring or b.) pressing a dial button to make it ring

[kiri]

You could do this with a Dual cordless phone set such as a BT trio/duo pack, no landline needed.

[videos]

Great video. Do you think this can work in an old pulse phone?

[KitMacAllister]

This hack also works with Wireless phones. You will need to supply power for the phones, but the line will still work without plugging it into a phone jack.

[homemadeyumies]

Can you make a video for multiple phones and to add a speaker

[vpleric]

Is there a how to video to add a ringer or led to these phones? 

[okamijubei]

That's neat but what if you want to hook up more than two phones for intercoms?

[warnematt]

holy shit, a project made without a microcontroller! resubbed.

[lumiredes]

Great, any ideas for a ringing sistem

[NemuiJin]

This is awesome. I wonder how long of a phone line this works with. Would've been a cool thing for neighborhood kids to talk to each other back before cell phones. We were always getting yelled at for tying up the phone line.