Posts Tagged ‘data packets’

How Does A Business Phone System Work? Part 2 – The Cables

April 5, 2009

Much of the time spent on designing and implementing VOIP phone system hardware concerns the PBX and the handsets. Think of the PBX as the brains of the system and the handsets as the hands and feet that are told what to do by the brain. How does the PBX signal the handsets to ring? To display certain features? To transmit the voice packets?

Simply put, the cables connecting the handsets to the PBX are the nerves of the system. They carry the signals back and forth across the network that comprises the vital infrastructure of the entire system. What types of cables are used and what should the typical business owner or manager know about them?

Because VOIP means Voice Over IP, the phone system will be running across the same network that the computer data packets use to share information with each other. In essence, the voice phone packets are similar to the computer data packets which is why this concept works in the first place.

The network cables are actually several strands of copper wiring that are twisted together in a regular pattern. The minimum specification for the VOIP cable demands an eight-wire cable where pairs of wires are twisted together as a four pair helix. Some wires carry the packets in one direction, others carry them the other way. Testing many years ago found that the twisted pairs must be so many twists per foot in order to carry the full signal as far as possible with maximum data yet minimal data loss. This is known as CAT5e data cable. There are some variations in cable jacketing such as PVC insulation (the most common) vs. plenum insulation (does not emit noxious gases when burned or heated). Plenum CAT5e cable is about three times the cost of PVC CAT5e cable but is a fire code requirement in most “Class A” buildings plus some other buildings where a shared plenum air space above the ceiling is found.

Older phone systems and residential lines most often use CAT3 cabling which is not suitable for computer use and thus cannot be used for VOIP transmissions. All cables are labeled on their insulation every so often with a sequence of printed tags that show what type of cable they are. It is easy to read those tags to see what type they happen to be. The insulation color does not matter. Any cable can be one of white, blue or many other colors.

CAT6 is one more variation that is designed for high speed networks. CAT6 cable is not necessary unless the entire network is gigabit speed and has a CAT6 minimum spec. Installing and verifying CAT6 cable is about twice the price of installing CAT5e.

There are two ways that cabling is used in an office. The main cabling is run from the phone board through the ceilings and walls to each location and is terminated at a walljack port. The second type of cable is the shorter patch cable that is plugged into the walljack and then run to the phones and/or computers. Patch cables are always PVC cable because they are not supposed to be used in ceilings. They should match the CAT5e/CAT6 rating of the ceiling cable.

Ask for your free phone system audit from Select Phone Solutions by calling 281-501-6464.

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