Introduction: VOIP Phone AND Intercom System

Picture of VOIP Phone AND Intercom System


The above instructable tells you how to use a Linksys VOIP box to connect to POTS phones together and make a sort of simple home intercom system. However, many people (myself included) wondered if additional phones could be added to this system if 2 or more VOIP boxes were on the network.
After some experimenting I was able to make this happen on my home network using a Linksys SPA-2012 and a Linksys SPA-1001, which gave me 3 phones that can all call each other.
Additional VOIP boxes could also be added for more phones.
Also, the SPA-1001 is not only connected to the home-network, but can also call out via my CallCentric account (or any other VOIP account..I just happen to use CallCentric)


I wanted a simple phone-system running from my kids treehouse to a little playhouse in the back. I had some basic phones I found at thrift-stores. I read various instructables telling me how to add a small bit of voltage to the phones to make them operable; however, this method did not have a way of making the phones ring.
Other people had some complex methods of adding a button connected to ringers and such, but nothing suited me.

Finally, I stumbled on this instructable:

I happened to have a Linksys two-line VOIP box sitting on the shelf, and dinkered around until I was able to get things working. And indeed it worked. The two lines were able to call each other, and I could program the dial-plan for specific keys (press 1 to call 1 to call playhouse)

Wonderful, but then I wanted more...I wanted my separate VOIP box in my work-shed to be able to call the treehouse and playhouse...and for them to call my shed, but I still wanted to be able to use my VOIP service to call out for long-distance.

After much experimenting, I was able to make it happen. Here is how:

Step 1: First Step: the Right Kind of VOIP Box

Picture of First Step: the Right Kind of VOIP Box

I mentioned that for this project, I originally started with this wonderful instructable:

My instructable is simply an addition to this

The only difference was that I used a Linksys SPA2102, while he used a Linksys PAP2T; however, the differences were few and I followed his instructions and things worked.
If you browse down to the comments on that instructable, there were some tips for dial-plans to make specific numbers for each phone. I followed those and was able to make 1 the dial-number for each phone to call the other.

The dial-plan is the very last field in the form to fill in. The code I ended up with looked like this:

(<1:> S0 <:treehouse@>) this goes in the dial-plan for the playhouse

(<1:> S0 <:playhouse@>) this goes in the dial-plan for the treehouse

see the screen-shot for a closer look.

Okay, so that gave me two wired phones with a VOIP box in between them that can call each-other by pressing 1.

Now I want to add another VOIP box in a different location on the property (my work-shed) that is connected to the same network, and can call out, but also press certain keys and call the playhouse and treehouse.

The VOIP box I use in my shed is a Linksys SPA-1001 (unlocked, of course). This little device is nifty because it not only can turn your regular POTS phone into a VOIP phone, but it also magically adds a second line to a single-line phone.
I had already set up the first line to my CallCentric account, using these instructions:

The second line I had forgotten about completely until I started trying to figure out a way to connect to my little home-phone-line system. Then it dawned on me that I might be able to make the second-line on this device the home network line.
With a little tweaking, I was able to do just that!

Step 2: Line 2 of the SPA-1001

Picture of Line 2 of the SPA-1001

So my SPA-1001 is connected to my router, and configured on line1 to use CallCentric for cheap long-distance phone-calls.
I want line2 to be connected to my home-phone system, so the kids can call my shed from the playhouse or treehouse.

So just to clarify:

  • the treehouse and playhouse are both connected to the SPA-2102
  • the SPA-2102 is connected to my home-router and has an IP address of
  • the phone in my shed is connected to the SPA-1001
  • the SPA-1001 is connected to the same home-router and has an IP address of
  • the IP address does not matter as long as it remains the same for each VOIP box
  • Line1 of my SPA-1001 is configured to work with CallCentric

First thing I did was go into the SPA-1001, under the admin user, on the Phone tab.

  • Default line is set to: Line 1
  • Line 2 Select Code is: #

Next I went into Line 2 tab. Set up is identical to configuration at:

The only difference is the dial-plan. Here is what works for me:

(<1:> S0 <:playhouse@>|<2:> S0 <:treehouse@>)

on the phone I have to first press: #

This switches me to "line2", and I can dial 1 or 2, which will call the playhouse or treehouse.

Next, I have to change the dial-plans for the treehouse and playhouse

Step 3: Dial Plans for Treehouse and Playhouse

Finally, I add the shed to the dial-plans for the treehouse and playhouse:

Playhouse dial-plan:

(<1:> S0 <:treehouse@>|<2:> S0 <:cottage@>)

Treehouse dial-plan:

(<1:> S0 <:playhouse@>|<2:> S0 <:cottage@>)

and that does it. Now all 3 phones can dial each-other, and my shed phone can still call out. I might buy another SPA-1001 for my wife to have a land-line that can call all three phones.

If you had property with several buildings, or rooms that were far away from each other, but the same home-network, you could easily create a home-phone system for each building/room. Unlocked SPA-1001s are cheap on ebay.

Someone also suggested that these phones could be made to call remote locations that were connected via VPN or port-forwarding. That would be kind of cool to work out because it could be a way to create a personal phone-system that extended to family and friends at various locations.


james.bowen2 (author)2017-01-21

The problem I experiencing it the calling phone is not detecting that the other phone has hung up.

craftclarity (author)2014-06-04

What, no pictures of the treehouse?

treehouse photo added. Interesting little note: no nails or screws are embedded into the tree. The platform just rests on the huge trunk and branches, and the walls and roof are sort of weaved together from branches.

About This Instructable




More by ghettocottage:Yet Another Kimchi RecipeVOIP Phone AND intercom systemRoof Sketches for Cob Playhouse
Add instructable to: