Monday, October 11, 2010

When Is A Channel Bank Necessary .... As Opposed To A PBX?

A channel bank is a seperate device that can be provisioned for almost any DS0 or data service. In the old days you did it by placing the correct type channel unit in a slot of the channel bank .... but now everything comes in one box. Hook a DS1 or two to the box and provision voice and or data out of the other side. Unlike the old days when a sub changes services you don’t need to send someone out there to swap out or recover a card .... you provision it remotely and send the sub a bill.

A channel bank converts a voice T1 circuit into 24 analog phone lines. Typically, to need a channel bank, you'll have an analog PBX with a voice T1 circuit from your long distance carrier (or local phone company) which is in digital multiplexed formats. The channel bank does the analog to digital conversion, and the 1 to 24 multiplexing. If you have a digital PBX, with a digital interface card, you won't need a channel bank.

A digital interface card will connect the voice T1 to the digital PBX. Channel banks are nearing the end of their life cycle as enterprises large enough to require a PBX will be purchasing digital PBX, not analog PBX. Channel banks can be used to hang analog telephone sets -- I saw that once in a phone room selling magazine subscriptions: T1 into channel bank, then 24 phones at desks for staff to make telemarketing calls. Channel banks are also used to connect to analog auto dialing equipment -- probably lots of them used in political campaigns. What's left of the telemarketing business will be migrating to SIP trunks and IP calls ... ultimately relegating the channel bank to the status of the 8-track tape player!

That said .... I wouldn't write off the channel bank any time soon. There are hundreds installed daily in small and medium sized business's. Mostly due to cost considerations but often also limitations and restrictions from existing wiring and/or hardware.

In these cases you basically install one small box such as the Adtran 850 channel bank .... connect a T1 .... and provision voice and data out of that single box. One box, one bill, one subscriber .... CLEC's love these things.

Now why would anyone choose a channel bank over a PBX? Besides the aforementioned cost and wiring/hardware limitations.

Personally, I wouldn't say you would choose a channel bank over a PBX, more like you would use a channel bank with an older (or newer) PBX. Older PBX's don't always support digital interfaces and would need a channel bank if you were to get a PRI to feed your PBX. Likewise a channel bank can take multiple analog circuits and output them as a digital interface for connection to a PBX or whatever you want to do, especially if that newer PBX only has digital interfaces and you only have analog coming in (for who knows what reason).

Another use for a channel bank would be if you had two PBXs to support but only one PRI. You could use a channel bank to split that single digital connection into two or more digital connections with any number of individual circuits to each. I suppose you could get a PRI (they are cheaper than buying 23 separate POTS lines) and use it for analog calls or for data use (modem or fax) and would then need the channel bank to break the PRI down. Of course you don't always need the channel bank for that either. I've a friend with a Cisco AS5200 at home that has two dual port T1 cards in it for it's dial-in connection. If you don't know what an AS5200 would be used for, think dial-up ISP; although they might have larger versions and lots of them.

If all of this is making your head spin .... and you are seriously looking for a voice/data solution for your business (any size business) .... I strongly recommend taking advantage of the free help available through Network Solutions . They'll do all the heavy lifting to find you a solution that makes the most business sense .... including costs with a low price guarantee.

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