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How does a channel bank work

crypticlabs
Posts: 3
 Member Since:
2010-10-21
Submitted by crypticlabs on Thu, 10/21/2010 - 1:12pm.

Hello,

Here is the setup - IP-PBX server with 2-port T1/PRI card. One port on the card is connected to our PRI and the other is connected to our Rhino channel bank. The channel bank is in turn connected to a 24 port patch panel of RJ-11 ports. Fax modems connect to this patch panel and send analog communications through the channel bank, which then digitizes the signals and sends them off to the server and then out our PRI. This much I understand.

What I can't seem to figure out is why is it that the PRI line can only use 23 channels (or is it trunks?) and uses the 24 for signaling yet the connection between the IP-PBX server and the channel bank allows for 24? Does the connection between the server and channel bank use 24 B channels, like the 23 B channels used in the PRI? Any info on this would be greatly appreciated.

Thanks,

Ralph.

‹ Signaling Type Phones are down every morning. Any Ideas? ›


SkykingOH
Posts: 9682
 Member Since:
2007-12-17
The connection to the
Thu, 10/21/2010 - 7:11pm

The connection to the channel bank uses "in band" signaling. Bits are "robbed" from the T1 channel to control hook condition and ring.

In a PRI the signaling is "out of band" and uses ISDN protocol on one T1 channel.

--

Scott

aka "Skyking"



crypticlabs
Posts: 3
 Member Since:
2010-10-21
@SkykingOH - minutes before
Thu, 10/21/2010 - 7:44pm

@SkykingOH - minutes before I read your response, I had finally found some information that seemed to answer my question:

http://www.cisco.com/en/US/docs/internetworking/technology/handbo...

" Channel Associated Signaling:
T1 Channel associated signaling (CAS) lines have 24 56K channels—part of each channel is borrowed for call signaling. This type of service is also called robbed-bit signaling. The E1 CAS still uses only the 16th channel for call signaling, but it uses the R2 international standard for analog call signals.
CAS is not an ISDN interface; it allows only analog calls to come into the access server. This is often done to allow an access server to work with a channel bank, and this scenario is seen more commonly in South America, Europe, and Asia."

So, my next question then is why is that the connection between channel bank and ip-pbx server is CAS and the PRI is not CAS (not sure what this is called, but referring to the method of 23 b channels and one d channel)?

Thanks,



crypticlabs
Posts: 3
 Member Since:
2010-10-21
I think I found the answer
Thu, 10/21/2010 - 7:57pm

I think I found the answer to my question. It seems PRI uses CCS and has benefits over CAS at the cost a channel . So I guess now, my question is why is it that the channel bank uses CAS over CCS?



SkykingOH
Posts: 9682
 Member Since:
2007-12-17
Quote: So I guess now, my
Thu, 10/21/2010 - 9:09pm
Quote:
So I guess now, my question is why is it that the channel bank uses CAS over CCS?

Because the analog extensions don't benefit from the ISDN feature set in the PRI.

--

Scott

aka "Skyking"



jfinstrom
Posts: 2013
 Member Since:
2007-03-07
Channel banks have 2 simple
Fri, 10/22/2010 - 8:36am

Channel banks have 2 simple tasks

1. If it is digital make it analog.
2. If it is analog make it digital.

They are meant to adapt old infrastructure and to easily extend infrastructure.

They "BANK CHANNELS"!

I have a pbx and I need to extend 72 users to another building. To do this I can run 144 wires or I can run 12 by putting them over a T1 in sets of 24. It makes more sense to run 12 wires which is less copper and greener if your in to that sort of thing.

Channel banks work great foe compact systems that do not displace a lot of heat. You can run a T1 in your system generating negligible heat and off load all the heat generated by FXS channels to another device.

--



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