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Articles and whitepapers 26/8/2003 Light Up Your Cable: A Quick Way To Identify Cable Runs By John W Aldous There are two aspects of a premise wiring system that can cause significant cost in both time and efficiency. The first is the time taken to identify the cable runs from outlet to the patch panel after the cable has been installed. Unlike equipment costs, which are relatively fixed, the cost of installation can change depending on the time and the cost of labour. Ask any cable installer who has had the experience of pulling bundles of cable through small areas to the communications room, what the most time-consuming part of their job is, and the answer is always the same - it's the long process of identifying each cable with its workstation. The second is the maintenance of the system such that the ports are still identified and the patch cord ends can easily and quickly be identified. How many installations' records have deteriorated over time, or are so poorly completed that a major problem is encountered when changes become necessary? Solutions Current methods are often frustrating. A tone generator can transmit crosstalk over eight other cables, and cable tags often fall off while being pulled through tight spaces, and can be easily incorrectly marked. The concept of using light to identify cables is not new. Cabling contractor Willam C. Fincher and his son Randy have been using LED lights in the form of modular plugs to identify cables, for some time. On one very large job, their firm, SCCI, saved three weeks of labour cost using their 'home-made' cable locator plugs. A patent was granted in 1998, and the technology is sold as the DataLite System kit. This kit includes a number of modular plugs with LEDs built-in. During installation, there is no need to label the cables before pulling and termination. Instead, the installer inserts these modular plugs into each port of the patch panels. Another installer would then use a power unit at the 'far end' to send power from the workstation to light up one of the LED modular plugs, thus identifying the port connected to that workstation. LEDs built into the Patch Panel Although the DataLite System offers a solution for identifying cables on a traditional patch panel, installers must still place the LED plugs into each of the patch panel ports, and may find themselves short of plugs in a large installation job. A new patent-pending solution, developed by Aldous Systems in cooperation with the patent licensee, places the LED onto the patch pane, and is called LCI (Light Cable Identification) technology.
How it works Very much like the DataLite System, patch panels with LCl technology give installers the freedom to begin pulling cables from workstations without having to label them. Installers can finish pulling all the cables to the communications room before starting the job of identifying them. This offers installers a more organised working environment because debris and obstacles can be cleaned away as the actual installation work is completed. To identify the cables, one worker simply walks from one workstation to the next plugging in the signal sender to the outlet and communicating via radio to the second installer in the communications room. The second installer identifies which LED on the patch panel lights up, records the connection, and the step is repeated. Problems with existing methods Tone Generators For decades, phone technicians and electricians have been using tone generators to quickly locate and identify phone lines and other electrical wiring. This method has been carried over to LAN cabling and, although it has been an acceptable practice for years, it does not work with the Cat5e and Cat6 network cable developed to support high bitrates. With these, cable pairs must be so precisely balanced and tuned at the higher frequencies in order to block noise at lower frequencies, that the lower tone generator frequencies are forced to the far-end as cross-talk across as many as eight other cables. Without actually touching the probe on the copper wire, it is nearly impossible to select the correct cable at the far end. Labelling Cables Cabling training instructors realised the problem several years ago and started teaching a method of tagging or marking the far end of the network cables prior to the pull through small spaces to the communications room. This is a time-consuming process that must be carried out with a tremendous amount of care. The tags must be marked correctly with the proper workstation designation, and attached securely - otherwise, problems and confusion will result at the far end. Further problems arise when contractors hire helpers or trainees to do the time-consuming work of marking cables, thus increasing the chance of mis-marked tags or tags coming off during the pull. Then, in order to start sequentially punching down the cable to the corresponding patch panel port as instructed in the training class, the cabling technician must find number '1' out of hundreds, or even over a thousand, lines. All of that time spent sequentially punching down the cable will be wasted later when additions, changes or moves are implemented and thus destroy the sequence. Performance Although one would think that, with an LED built into a passive device, the performance would be affected, tests show that the performance of patch panels with and without LCI technology are virtually identical, as shown in the charts and table below.
Table 1 - Cable headroom with and without LCI
Technology
The test configuration for both the Return Loss and NEXT were setup according to the TIA-EIA-568-B.2-1 final specifications utilising 90 meters of Cat6 horizontal cables. The test equipment used was an HP 8152C Network Analyser. In each test, the performances of the patch panel with and without LCI technology are identical within tolerance, and both easily exceeded Cat6 requirements. How much time and money is actually saved? Because patch panels with LCI technology are not yet available, a documented case history of the DataLite System can be used instead, due to the similarities of its usage. It should be remembered that the DataLite System is used on standard patch panels, and so requires the extra step of inserting the modular LED plugs. The time saving of using patch panels with LCI technology therefore, would be even greater. Table 2 shows data obtained by Structured Communications Cabling at Harris Hospital where cables are installed to 500 workstations.
Table 2 - comparison of cable identification
costs using a tone generator and LED technology
The above example shows that using LED technology results in a cost saving of £50 per patch panel. In some cases, this is more than half the cost of the patch panel. The cost of the patch panel with LCI technology is on average approximately 20% above the conventional panel cost, but this is more than compensated for in the potential cost savings. Patch Cords Identification To remove this problem permanently, the simple use of light technology can be used to identify ends of patch cords. How many installers or end-users have experienced difficulty and frustration in identifying patch cord ends where the labels have been damaged or are missing, and they are installed in a high density? By the use of a fibre optic 'loop' integrated into the patch cord, this problem is removed permanently. The principle of the PatchSee system can be see in Figure 4.
The use of the specially-designed torch provides the light transmission into one end of the RJ45 plug. The other end of the patch cord is very easily identified by the twin spots of light showing on the rearward face of the plug. This innovative product contributes added value to both the installer and the end user. Summary LCI technology brings significant benefits to installers and end users of premise cabling systems, by offering significant savings in terms of time and money, both during the installation and beyond. It makes cable identification easy and error-free, and has no adverse effects on cable performance. John W Aldous is Managing Director of Aldous Systems (Europe) Ltd.
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