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DESIGNING THE CABLING ROOMS (IDFs) FOR VOICE-OVER-IP TELEPHONE
By Larry Smith, President, ABR Consulting Group, Inc.

You can no longer avoid the increasing switch to digital telephone systems (Voice-Over-IP).  We see more and more being considered and installed.  It's a trend that will never reverse back to analog.  We have been designing cabling systems for the eventuality of VoIP for about 3 years.  Here's a summary of our basic design changes:

1)   All voice and data station cables are terminated onto the data racks (rack-mounted RJ-45 patch panels).  Voice station cables are no longer terminated on the backboard.  With the data switch and now VoIP switch being rack-mounted, this permits any of the station cables to be used for voice or data.  

2)   The cabling rooms themselves are more rectangular to accommodate more side-by-side racks.  More racks are necessary to land all of the station cables (remember the voice cables used to land on the backboard).  

3)  Where VoIP systems will be installed, we now minimize the riser backbone copper pairs.  Digital telephone runs on the riser fiber pairs.  Where VoIP is in the future, we run the normal compliment of riser backbone copper pairs and terminate them on the backboard.  

4)   We then run 25-pair copper cables from the data racks to termination hardware adjacent to the riser backbone copper termination hardware.  This only has to be Cat 3 rated since it's just for voice.  On the data racks, you terminate these 25-pair cables on Cat 3 or Cat 5 patch panels.  Thus, when we cross-connect, all data cable patch to the data switch.  All voice cables are patched to the backbone patch panels on the data racks and then again at the riser termination area.  Once, VoIP is installed, this cabling system between the data racks and the backboard goes away.  

5)  All voice and data cables are rated no less that Cat 5 as VoIP systems will not run on anything less.  In today's buildings were are normally installing Cat 6 and occasionally, Cat 5e.  

Now, we need to get caught up with the UPS for the cabling rooms.  Most cabling rooms are not on the building UPS.  Guess what.  VoIP systems in the cabling rooms will go down with a loss of power.  This is a very foreign concept to users who are either on Centrex or a PBX with a 4-6 hour battery.  During a loss of power, you've always been able to pick up your phone and use it.  No longer.  When designing your new building or modifying your existing building, you must now include UPS power to your cabling rooms in your design specifications.  You must also now include the calculations for these systems into the projected load to be placed on the UPS.  

Finally, we suggest that you consider using the analog lines for your fax, Polycom and other analog devices for your emergency phones.  This means keeping them on copper circuits and not on the VoIP phone system.  The tradeoffs are worth it.  Once you see how VoIP works, there's no turning back.     

 Contact us at www.abrconsulting.com  Phone:  925.872.5523