VG248 FXS to punchdown block

Unanswered Question
Nov 9th, 2007

Please forgive my nieveity on this, particularity the analog side of the question.

We are looking into a way to remove all the remaining POTS lines from our building. Currently, the only lines that remain in use are Fax, Modem, and direct dial buttons for emergency service in elevators. All of our other phones are run off of call manager 5.1 on SCCP protocol.

I was looking over the VG248 and it would appear to be the solution to bring the analog lines over; however, there is one caveat I am having a hard time finding an answer to.

Currently, all of our Centrex/Pots lines come in to a punch down demark from our analog line voice provider. They then go to a second punch down block before going off to various phone closets in the building for distribution. We do not have a PBX or legacy voice mail systems as any of those tasks are handled by the provider.

Retaining the current numbers is not needed, nor any of the other services that may been on those lines needed, as they could be generated/configured similarly once in call manager.

The VG248 uses FXS out ports for the lines and this is where my problem lies. I cannot seem to find how one would convert the FXS outputs to link them to the punch down block that leads out into the building. If at all possible we are looking to keep the current phone wiring that runs throughout the building from the second punch down block outward.

Any help you could provide in pointing me in the right direction would be greatly appreciated.


I have this problem too.
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rob.huffman Fri, 11/09/2007 - 10:11

***Posted on IP Telephony Forum as well***

Hi John,

Excellent question here! We use a number of VG248's and really like the product. The way that they "wire out" with RJ21 25 pair cables really fits nicely into most wiring infrastructures.

You can order most any length of pre-made 25pr cable that will connect to the Front Panel of the VG248 and can be routed right to the existing cross-connect (punch down blocks) or you can terminate (on punch down blocks, Bix,110 Blocks,R266) the VG248 25 pr cables in a Central location and run a new Tie Cable or Cables to the existing cross-connect. The "old" Analog circuits can be traced and new connctions to the VG248 can easily replace them pair for pair, circuit for circuit. This is nice for a "phased" approach :)

We have migarted hundreds of Analog lines from Nortel to the VG248 in just this manner. Using the type of cable listed below;

Cisco RJ21 Cables

Hope this makes sense!


Tommer Catlin Mon, 03/31/2008 - 12:22

Hey rob, do you know on the punchdown from the RJ21, is it standard? or do they need to skip the first binding post or something like. I thought it was something different in the cabling to the 66 block.


rob.huffman Mon, 03/31/2008 - 13:02

Hey Tommer,

Long time my friend :) The punchdown on the R66 Block is standard (pair for pair) When running your jumpers only pairs 1-24 are used as pair 25 has no associated port coming from the VG.

Hope this helps!


Tommer Catlin Mon, 03/31/2008 - 13:07

Yes yes my friend... ehlo! I think I found someone elses problem. I thought maybe they had punched down the pairs wrong, but after looking at the config, someone had added in "IP routing" and that was throwing it off. I added in a static route ip route x.x.x.x and automagically worked. It's odd because everything was registered, etc.

ccbootcamp Mon, 11/26/2007 - 22:32

Old SCSI cables do the trick my friend. I have used them a bunch of times for my VG248s. Same connector. Or, you can use the old Catalyst 5000 telco cables and break them apart. Either one works well.



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