[VoIP] Channel Banks

[Rusty Dekema]

On 3/22/07, Russ Price <kxt at fubegra.net> wrote:
> Jayson Smith wrote:
> 5. The T1 card for the computer will cost far more than the second-hand
> channel bank.

If you are willing to muck about with Cisco equipment, there is a
(sort of) cheap way to get around this by buying a (used) Cisco
MC3810. It comes with a T1 card (onboard) that can be connected to an
Adtran (or any other T1-based) channel bank, and it will* trunk these
channels back to an Asterisk machine via SIP over its onboard ethernet
port.

The " *see store for details " bit here is that you need an IOS image
(the software set for the MC3810) that is capable of doing SIP/RTP,
which not all of them are. Unless you buy an expensive support
contract from Cisco, they will not supply you with updated IOS images.
To my knowledge, you can't even plunk down money to buy one -- you
have to have the support contract. It is difficult, though not
impossible, to obtain unauthorized (pirated) copies of IOS images on
the Internet, so the best way to do this is to have a friend who
already has an MC3810 with the proper IOS load give you a copy. Of
course that's not entirely kosher either, so whether this is a
workable solution will depend on your views on such matters...

The upside is that you can get an MC3810 very cheaply -- well under
$100 if you look around on eBay and are patient -- and the MC3810s can
also take all kinds of other cards in addition to the builtin T1 and
Ethernet: FXS, FXO, E&M, second T1 module, etc.

My roommate operates an MC3810 to trunk between his channel bank and
Asterisk machine, and he found that the IOS image he has that supports
SIP requires 64 megabytes of RAM. There is only one slot for RAM on
the MC3810, so you will need a 64 meg 72-pin SIMM, which you may not
have sitting in your collection, but is easily available on eBay. I
forget whether the 3810 requires Parity or EDO RAM, but I can find out
if anyone wants to know. One other caveat is that in order to accept a
64 MB SIMM, your MC3810 may require an updated boot ROM. I am not sure
what this process entails (replacing a socketed chip, or just flashing
it), but again, I can find out from my roommate as he had to do this
in order to get his to work.

So, in the end, it is a lot of hassle to use an MC3810 for this if
you're not interested in the details of Cisco equipment, but it can
also be a pretty cheap and fun, for some values of fun, way to connect
a channel bank to an Asterisk system.

Rusty