Balancing Act

Reel Time February 2009, Cabling Business Magazine

Three twisted pairs
by Carol Everett Oliver, RCDD, of Berk-Tek, a Nexans Company
Q:  What does it mean for cable to be balanced? 
A:  UTP cable has become the dominant medium in data communications, but UTP systems depend on electrical balance between signals transmitted over each pair.  Simply put, twisted-pair cable is a “balanced” media because the system is designed to cancel electrical interference based on the pair’s physical symmetry – or “balance” between each other.  The conductors of the pair should be manufactured identical to each other and twisted at the same rate over the length of the cable.  When this occurs, the data current and voltage of each conductor is equal magnitude, but in opposite polarity. Unwanted coupled noise will be of equal levels, same polarity, on  each conductor which allows for its cancellation by the receiving equipment  .
Cable balance is an important parameter for high-speed computer network reliability as the better the balance between the conductors of a pair, the greater the reduction in noise within the pairs as well as external EMI and RFI.  
Without balanced pairs, interferences including crosstalk and noise will basically degrade the cable signal and ultimately the system performance.  Examples of noise sources include power lines and electrical equipment, alien crosstalk from other cables, cell phones, radio and radar stations and even fluorescent light fixtures.  As a UTP channel is being applied in more and more environments and as data network speeds increase, balance is becoming a critical parameter to the operation of the cabling system.

Read the article in full...Balancing Act, Reel Time, February 2009

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Carol Oliver Berk-Tek Marketing Analyst