Hack63.Build a Bat Phone

Hack 63. Build a Bat Phone

Do you think Bruce Wayne uses VoIP to receive emergency calls from the Mayor of Gotham? Of course he does. He's that cool (his car is OK, too).

If you've worked your way through "Tweak Your Sipura ATA" [Hack #62], you know Sipura Technology makes some very powerful and flexible ATAs. So powerful, in fact, that you can use them to set up a point-to-point "hot line" with no SIP proxies or registrars.

A "bat phone" (or automatic ring-through in the telco world) is best known from the popular Batman television series. Batman would have such a burning desire to speak with the commissioner that he didn't even have time to dial. The simple act of picking up the phone automatically connected him to the designated remote station.

Here is what you will need to get this going with your two Sipuras:

Two Sipura ATAs

As of this writing, the 841, 1000, 1001, 2100, 2000, and 3000 were widely available, but Sipura has just been acquired by Cisco, so these model numbers could change.

Static IP addresses or dynamic DNS

Each Sipura will need to know where the other is. On a simple LAN, this is incredibly easy. Just assign static IP addresses, and move on. Over the Internet, behind NAT and/or firewalls, this task can get complicated. While it's too much to cover here, you will want to look into port forwarding and dynamic DNS.

5.6.1. First Things First

Take out one of your shiny new Sipuras. This will be called ATA1. Connect the phone (to line 1 if you have more than one line) and Ethernet cables. Then connect the power. If your LAN uses DHCP, the Sipura will acquire its IP address using DHCP. If you pick up your telephone, you should here a dial tone. Enter ****. You should hear a not-so-friendly voice say the words "Sipura configuration menu." At this point, you should enter 110#. The same "friendly" voice should come back and read you your IP address. Make a note of it.

While DHCP does make it easier to attach new devices, it makes it harder to keep track of them. Once you get into the web interface, you should assign a static address, or use the static mapping features of your DHCP server to assign the ATAs the same IP addresses at all times.

After you have made note of the IP address for ATA1, repeat the process for your other Sipura, ATA2. For the rest of this hack, we'll assume ATA1 and ATA2 have the respective IP addresses 192.168.1.101 and 192.168.1.102.

After you have the IP addresses of your Sipura devices, fire up a web browser on a machine connected to the same LAN. Using your web browser, enter the IP address of ATA1. You should see a gray screen filled with status information. Open another window (or tab) and enter the IP address of ATA2. You should see a similar (if not identical) screen, with the exception of the different IP addresses. Now we're ready to have some real fun!

5.6.2. Configure the Sipuras

The dial plan on the Sipura ATAs is one of the more attractive features of the SPA line of products [Hack #62]. It is the dial plan that is going to make this hack possible. In your web browser for ATA1, click on the Admin link in the top right-hand corner. You should see several more options become available. Then click Advanced. You should see even more options become available.

Next, click the Line 1 tab and scroll down to Username. Enter ata1. Do the same for Display Name. Scroll down to Dial Plan. In the Dial Plan edit box, erase what is currently there and replace it with the following:

 (S0<:ata2@192.168.0.102:5060>) 

Save your changes. Now, for ATA2. Switch over to the ATA2 browser window, and click Admin and Advanced again. Now, move over to the Line 1 tab, and down to Username and Display Name. Fill in ata2 for both. Again, scroll down and fill the Dial Plan box, this time using the values for ATA1:

 (S0<:ata1@192.168.0.101:5060>) 

Again, save your changes. Now, any time you pickup either phone connected to line 1 on ATA1 or ATA2, it will automatically call the phone attached to line 1 on the other ATA.

5.6.3. Hacking the Hack

Nothing says "Holy phone mod, Batman!" like a bright-red rotary-dial phone with the mechanical dial wheel removed. Replicas of such phones are actually available on eBay, as are plans to build ones that have flashing lights, too. But for this hack, all you really need to do for an authentic red bat phone^[1] is the following:

^[1] I've since learned that "true" bat phones not only are red, but must also reside in a glass cake cover when not in use.

1. Find a cheap, old rotary-dial phone at a garage sale or in the attic.

2. Remove the dial wheel and discard it.

3. Carefully remove the electromechanical guts of the phone and set them aside.

4. Use some bright-red, plastic-friendly Krylon Fusion spray paint to turn that vintage monster red, like a tomato. Allow it to dry, of course.

5. Put the phone guts back into the newly blushing enclosure, reconnect to your Sipura bat phone ATAs, and use that hotline to your heart's content.

Kristian Kielhofner