[VoIP] Channel Banks

[Shane Young]

This is definately "cheaper" than a T1 board, but you are still doing  
SIP rather than local channels on the system.

For most people it doesn't really matter either way.  The nice thing  
about not using a SIP device is that you don't have to build dial  
plans in two locations.

With a SIP device, you have to give it a digit map of some sort.  The  
SIP device will collect the digits until it has decided you are done  
dialing, then send the call to the Asterisk system.

Building complex digit maps on the Cisco devices can be a headache  
particularly if you are a stickler about having the called party start  
ringing immediately after you have un-pressed that seventh digit :)

The adtran banks sound like a good product.  I have used a lot of  
Carrier Access channel banks, mostly the Access Bank 1 and ADIT 600.

The Access Bank 1 goes for about $100 on ebay.  It has two card slots.  
  You can have 24 FXS or 24 FXO or 12 FXS and 12 FXO.

There was a card which had some of each, but I've never tried one.

The Adit 600 is very similar to the Adtran 750 and 850.  You have 6  
card slots and each card has 8 FXS or 8FXO cards.  I have one with 5  
FXS and 1 FXI card.

The FXO cards can be configured for DPT and can be connected to Tip  
and Ring of an incoming selector on a step switch.  They will then  
recognize the polarity reversal (answer) and Asterisk will see that too.

For Jayson, the best thing I could reccomend is to keep your eye out  
for a good deal on a working channel bank and save up for a T1 card.   
It wouldn't supprize me to see the older T1 cards drop to $200-$300 in  
the next year.



Quoting Rusty Dekema <rdekema at gmail.com>:

> 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
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--Shane
+1-821-7311 CNET