It has been common for an electrical contractor to install the cabling that a library requires for its automation activities. However, changes in cabling requirements brought about by the need to accommodate greater data transfer rates make it increasingly important that experienced data cabling installers be used.
Category 5 UTP (unshielded twisted pair) may look like the Category 3 used in past years, but it is quite different as it can accommodate up to 100 Mbps, rather than just 16 Mbps. But as good as Category 5 cabling is, its performance depends on the expertise of the installer. If the installer does not maintain tight twists at termination points, excessive near-end crosstalk (NEXT) may occur, resulting in impaired data communications and a significant number of errors.
In addition, for a link to be rated Category 5, all components in the link must be rated Category 5. For example, Category 5 cable, patch cords, and punch blocks that have Category 3 connectors will deliver only Category 3 performance.
One more caution about Category 5 UTP is delay skew, the maximum difference between the time a signal enters the transmission channel and the time it is received. Signals transmitted on the four pairs at the same time from one end should arrive at about the same time at the far end. 100BASE-T2, 100BASE-T4, and 100VG-AnyLAN use multiple cable pairs simultaneously to maximize bandwidth and lower radiated emissions. These technologies are able to reconstitute the original signal at the receiver only if the "pieces" arrive at about the same time. Some mixed-dielectric Category 5 cables, the so-called 3+1 and 2+2 cables, may have excessive delay skew, in which case multiple-pair, high-speed network signals cannot be recombined easily, and excessive errors or failure can occur. To avoid this, choose a cable that has a 100-meter skew of less than 40 nanoseconds (ns).
When looking for a contractor to install data cabling, choose one whose primary business is data cabling, not electrical wiring. If the company is a large one that does both, make sure that the division doing the work uses only experienced data cabling installers.