Overview
There is naturally a requirement for structured cabling for your new Computer system. This falls into two categories, the cables needed for data (to physically transmit data from a workstation or terminal to the server or printers) and power cabling (to physically provide a clean power source to these devices). A data point plus a double mains power socket needs to be provided for each Workstation, terminal, server or printer that will be used in your network.

Cabling & Mains Power Socket Installation Service
Our company can provide a complete cabling service to the outlines detailed here which removes the headache of conformity or dealing with local contractors whose knowledge & standards may or may not be adequate for the job. A written estimate can be supplied upon request. If however you decide you would rather contract the work locally, the guidelines for cable testing below will assist you in ensuring a smooth installation to the required standards.

Network Cabling Requirements
There are many cabling companies working at present to this basic Category 5 (CAT5) standard. The quality of the cabling used unfortunately varies widely within the scope of the current ratified BICC (British Institute of Cabling Contractors) CAT5 Standard. Poor cabling will cripple a network and is responsible for many of the intermittent problems experienced in their use. Problems of this sort are often hard or impossible to detect, leaving you with a major problem.

To prevent such potential problems in network communication, more advanced cable contractors use newer developments in cabling technology to achieve maximum data integrity.

The latest cabling is called CAT5E & CAT6. The reason that these cables are so secure is a matter of shielding. The cable core is perfectly protected from outside electrical interference by the density of its covering or 'shield'. Likewise over a long distance no data transmitted through the cable is lost via leakage (Near End Crosstalk & Far End Crosstalk) because the shielding prevents it therefore ensuring that the data you transmit from the source arrives at the destination without loss of integrity. Continuity of data transmission speed is also ensured.

Cabling Installation Workmanship Considerations
Enhanced cabling systems (CAT5E & CAT 6) offer tremendous advantages in performance over early Category 5 offerings. The danger is that component performance is so good it tends to mask poor installation practices. Where early CAT 5 cable had to be installed carefully to pass a Category 5 certification test, the newer products can pass the same certification test with ease but does not guarantee you are getting the performance you require or are paying for. Since today's Category 5 certification test does not fully test the capabilities of enhanced cabling systems, it is extremely important to adhere to good installation practices. Following proper installation techniques goes a long way to insure the wiring will support the demands of tomorrow's network. You must therefore ensure that the following tests are carried out by your cabling contractor and a Certificate of Conformity is issued by them verifying that your network cabling meets the required standard.
 
FOR THE INSTALLER - Data Cabling Tests and Cable Certification
Today's high-speed networks require, as a minimum, a Category 5 level of performance from the cabling infrastructure. Currently, Category 5 certification requires testing the cabling/electrical parameters to 100 MHz.

What to Test for when Testing Enhanced CAT 5E & CAT 6 Links
The following tests are recommended for performance analysis of enhanced cabling links to a CAT 5E or CAT 6 level and they can help establish the relative electrical performance of the cabling system. These tests are additional to those established for certification to basic CAT 5 standard. Extend the test frequency to 250 MHz
Some of the newest field testers on the market have the ability to sweep test frequencies well beyond CAT 5's 100 MHz. If you are using a tester with that kind of power, take advantage of the information it can provide.

Test for Headroom
A simple comparison can be made between measured cable performance and establish Category 5 standards. This measurement is typically referred to as "Headroom" or "Margin". Headroom is the calculated difference between established Crosstalk limits and the actual test results. More headroom (higher number in decibels, or dB) equates to higher cabling performance.
 
Attenuation to Crosstalk Ratio (ACR)
ACR is not specifically a new test, but rather a relative comparison between NEXT and Attenuation performance. Expressed in decibels (dB) the ratio is the arithmetic difference between NEXT and Attenuation. ACR is significant because it is more telling of cable performance than NEXT or Attenuation alone. ACR is a measure of the strength of a signal compared to the Crosstalk noise.

Propagation Delay/Delay Skew
Measured in nanoseconds, Delay quantifies the time it takes for an electrical signal to travel from the transmitter to the receive end. Delay Skew is the difference in delay on the four wire pairs. Excessive Delay or Delay Skew will adversely affect network performance, particularly in transmission schemes where it is necessary for data signals to arrive nearly simultaneously such as Ethernet.

PowerSum NEXT
PowerSum (in dB) is calculated from the six measured pair-to-pair Crosstalk results. PowerSum NEXT differs from pair-to-pair NEXT by determining the Crosstalk induced on a given wire pair from 3 disturbing pairs. This methodology is critical for support of transmissions that utilise all four wire pairs such as Gigabit Ethernet.

Return Loss
Return Loss (in dB) is a measure of the impedance consistency in a cable. Impedance variances, if excessive, will cause unwanted signal reflections or "echo" which can interfere with the transmitted signal.

Far End Crosstalk
Far End Crosstalk or FEXT is similar in nature to NEXT, but Crosstalk is measured at the opposite end from the transmitted signal. FEXT tests are affected by signal Attenuation to a much greater degree than NEXT since FEXT is measured at the far end of the cabling link where signal Attenuation is greatest. Therefore, FEXT measurements are a more significant indicator of cable performance if Attenuation is accounted for. The comparative measurement of FEXT and Attenuation is called Equal Level Far End Crosstalk or ELFEXT. Characterising ELFEXT is important for cabling links intended to support 4 pair, full-duplex network transmissions.
 
Category 5E folds these new tests into the mix with those already mandated, providing additional cable performance information above Category 5. Category 6 takes matters one step further by extending the swept frequency testing out to 200 MHz, twice the required 100 MHz frequency for today's Category 5.

Higher frequency testing, coupled with the new measurement parameters, means Category 6 compliance requires excellent performance from the cabling system. Cable and components must be "matched" for the entire end-to-end link (channel) in order to meet the more stringent standard. It will no longer be acceptable to randomly mix and match components if trying to achieve Category 6 compliance. Beyond component selection, installation methodologies and workmanship will have an even greater impact on link performance, demanding an increased awareness and high skill level from installers.

Wire Map
Wire Map consists of determining a terminated cables end-to-end connectivity. Wire Map also detects physical opens or shorts in the cabling and provides an indication that the correct pairing of twisted pairs has been maintained.

Length
This is the electrical cable length of the segment under test. Length measurements are necessary to insure the cabling link has not exceeded the allowed maximum. Exceeding the maximum length limit for the end-to-end link may result in excessive propagation delay and/or attenuation resulting in poor network performance.

Attenuation
Attenuation, measure in decibels (dB) is a measure of signal loss in the cable. As the signal travels further from the source of transmission, it weakens. If the signal is sufficiently weakened (attenuated), it may become unreadable at the receiving end. Attenuation increases with the length of the cable, the frequency at which data is transmitted, and to some degree, the cable temperature.

Near End Crosstalk (NEXT)
NEXT measurements (in dB) indicate the degree to which unwanted signals are coupled onto adjacent wire pairs. This unwanted "bleeding over" of a signal from one wire pair to another can disturb or distort the desired signal. As the name implies, NEXT is measured at the "Near End" or the end closest to the transmitted signal. NEXT is a "pair-to-pair" reading where each wire pair is tested for Crosstalk relative to another pair. NEXT increases as the frequency of transmission increases.

While these four parameters are an adequate measure of performance for today's network demands, more sophisticated data transmission schemes will drive the need for more sophisticated cabling certification techniques. This in turn will drive the need for more sophisticated field testers. Recently developed field testers are being offered with frequencies exceeding 200 MHz and incorporating new cable test parameters. These next generation testers are far more complex and powerful than first generation Category 5 testers and will be a vital part of future certifications that exceed Category 5. Certification beyond Category 5 will require compliance testing of existing parameters as well as several new parameters.

Test for Attenuation to Crosstalk Ratio (ACR)
ACR is the calculated difference between Crosstalk and Attenuation measurements and is indicative of the useable bandwidth of the cable. Of particular interest is the frequency (in MHz) at which the ACR value is equal to 10 dB. 10 dB is widely accepted as the minimum ACR value for effective data transmissions while maintaining a reasonably low network Bit-Error-Rate (BER). A cable that has an ACR value of 10 dB at 185 MHz has significantly better performance than a cable with a 10 dB ACR at 100 MHz (current CAT 5 limit). Category 6 proposes a 10 dB minimum ACR value at 200 MHz. It makes sense then to test to at least 200 MHz (IEEE recommends testing to 250 MHz) looking for at least 10dB ACR at 200 MHz.

Test using PowerSum
Since upcoming network standards will most likely utilise all four wire pairs for full duplex transmission, it is important to utilise the PowerSum capabilities of the field tester. This will insure that multi-disturber Crosstalk is at least within acceptable limits set by CAT 5.
Test for Propagation Delay and Delay Skew

These results can be compared to the draft requirements for Category 5E and Category 6.

Mains Electrical Power
Computers are very sensitive electrostatic devices and are dependent on a clean source of power for proper operation. Many network problems experienced are due to fluctuations in the power supply. For example, when you switch on a vacuum cleaner or a washing machine, if a computer is plugged into the same ring main the resultant surge or sag in electrical current can disrupt its normal operation perhaps to the point of physically damaging it or corrupting its data.

To prevent this from happening we recommend that a new clean ring main be fitted to your existing power supply that only the computers will use. This is our normal mode of practice and all sockets are colour coded red so that no one can accidentally tap into your computers power source. There should be a double power socket provided for each workstation, terminal, server or printer. These will normally be fitted next to the data cable point. Multi plug adaptors or 'chocolate block' adaptor strips may not be used under any circumstances.

Site Plan
To implement an effective cabling scheme it is important that the cablers have a clear site plan to work from. This merely needs to be a plan view of your site with markings on it to indicate the termination positions of the cables you need installed. Normally you will have the plans to your building which will be very accurate or you can draw a simple scale line art drawing and mark the points clearly on that. We will need this plan before cabling can commence.