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MAKING A CASE FOR 3-CABLE STATION RUNS
By Larry Smith, President, ABR Consulting Group, Inc.

In the past several years, it has been a standard to run 2 voice and 2 data cables to each end-user outlet.  The reason is that voice cables were placed on the backboard and the data cables were placed on rack-mounted patch panels.  With the cabling design being changed because of voice-over-IP telephone systems (see Designing Cabling Rooms (IDFs) for Voice-Over-IP Telephone), we now recommend that you specify 3 cables to each end-user outlet instead of 4.  

Here's the story.  The term 2 + 2 cabling implies that 2 cables will be for voice and 2 cables will be for data.  This is an older concept that was in use when the voice cables terminated on the wall and the data cables terminated on the data racks.  It was also a time when the voice cables were Category 3 and the data cables were no less that Category 5.  The cable jackets were often of different colors to distinguish between the cables.  Because it couldn’t be projected where more than one phone line or more than one data line was needed, the 2 + 2 cabling concept evolved.  It has become an accepted standard. 

Today’s cabling architecture is changing and is being driven by impending installations of voice-over-IP equipment.  VoIP requires a cable rated at no less than Category 5.  With VoIP equipment installed on a rack in a manner similar to data switches, all voice and data station cables are terminated on the data racks.  Voice cables are no longer terminated on the backboard but there is a connection to the backboard from the data racks to pick up the riser copper backbone which is still terminated on the backboard. 

With all station cables terminated together on the data racks, the question becomes – “Why do we need 4 cables?”.  Except for rare circumstances in a building installation, we never did need 4 cables; it was the reasons above that dictated the 4 cables.  With the ability to now place 3 identical cables together than can be used for either voice or data, where is the business requirement for 4 cables to each workstation?  it is our opinion that 3 cables for voice and data will serve your installation well.  Should there be an area that needs more, simply add another outlet.  This is far less expensive that providing the fourth cable to each workstation. 

 Contact us at www.abrconsulting.com  Phone:  925.872.5523