National and international requirements have been agreed through the standards ISO/IEC 11801 and EN 50173, which fortunately are identical with respect to link specifications.
The benefits for the end user are evident. He can let the link requirements in the above standards form the contractual conditions for accepting the final installation, he does not depend on supplier warranties to secure transmission performance, he can have a large extent of supplier and installer independence, and he will get highest possible quality just by claiming an installation acceptance testing. Which supplier or installer would risk a re-cabling by failing a final installation testing.

Today's problem is not link requirements, which are generally clear (except maybe for the different definitions of links, basic links, horizontal links and channels, which will be discussed in a future 3P Newsletter). The main obstacle has been and still is how to make a fast and reliable verification of a "Class D" installation (going to 100 MHz). Two different methods may be applied:

Measurements with laboratory equipment (Network Analyzers, etc.)
Measurements with hand-held field testers

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Measurements with laboratory equipment

Link measurements with laboratory equipment may be performed accurately by the very experienced operator, but it is a slow, difficult and unpractical way to demonstrate performance. A few very tricky pitfalls exist if you are not experienced in measuring short lengths of cable, for instance with respect to impedance measurements. However, it is outside the scope of the present 3P Newsletter to discuss details of link testing with laboratory equipment.
3P recommends, that laboratory equipment is only used:

to verify performance in case of disputes.
to demonstrate performance on a limited statistical basis.
to verify precision of hand-held testers.

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Measurements with hand-held field testers

Link measurements with hand-held testers can be performed fast by a trained operator allowing a 100 % verification of all links of an installation. Testers for "Class D" installations have been available for approx. 2 years, but quality of some early testers has been questionable, both with respect to precision and extent of testing performed. Still most testers only perform verification of some of the specified requirements. Low quality testers may both accept bad installations and reject good installations. The first point normally makes everyone happy (i.e. maybe only until traffic on the network is later stressed or transmission rate is increased), while the second point may create a million dollar panic without reason.

Quality of testers has been continuously improved by the manufacturers and parallel work in development of a specification for hand-held testers has just been completed. The resulting document, TIA telecommunications Service Bulletin TSB 67, has just been agreed and specifies two different quality levels of testers, i.e. Accuracy Level I and Accuracy Level II testers. Performance of Level II testers is the best, and some early model testers would probably have difficulties even in passing the Level I requirements.