One of the test parameters used when testing Category 5E or Category 6 UTP, FTP or ScTP Permanent Links or channels. For Permanent Link tests, the length should not exceed 90 metres, and for Channel tests the length should not exceed 100 metres. Before testing a site, an important factor to remember is that you have to set up the NVP for the cable. The NVP, or Nominal Velocity of Propagation is a value that the tester uses in its calculation of the cable length. A signal is sent down the length of cable and the measured time (propagation delay) is then multiplied by the NVP value to determine the length of cable. The NVP value is unique to each cable manufacturer, and you should check with them what the value is for their cable. The default NVP on most testers is 72%, but most of the locally produced cable differs from this, so please check it first.