the time it takes for the signal to be sent from one end and received by the other end. Delay Skew The Delay Skew test is used to find the difference in propagation delay between the fastest and slowest set of wire pairs. An ideal skew is between 25 and 50 nanoseconds over a 100-meter cable. The lower this skew the better; less than 25 ns is excellent, but 45 to 50 ns is marginal. (Traveling between 50% and 80% of the speed of light, an electronic wave requires between 417 and 667 ns to traverse a 100-meter cable. Cable Length The Cable Length test verifies that the copper cable from the transmitter to receiver does not exceed the maximum recommended distance of 100 meters in a 10BASE-T/100BASE-TX/1000BASE-T network. Insertion Loss Insertion loss, also referred to as attenuation, refers to the loss of signal strength at the far end of a line compared to the signal that was introduced into the line. This loss is due to the electrical resistance of the copper cable, the loss of energy through the cable insulation, and impedance mismatches introduced at the connectors. Insertion loss is usually expressed in decibels dB. Insertion loss increases with distance and frequency. For every 3 dB of loss, signal power is reduced by a factor of and signal amplitude is reduced by a factor of . Return Loss Return Loss is the measurement (in dB) of the amount of signal that is reflected back toward the transmitter. The reflection of the signal is caused by the variations of impedance in the connectors and cable and is usually attributed to a poorly terminated wire. The greater the variation in impedance, the greater the return loss reading. If 3 pairs of wire pass by a substantial amount, but the 4 pair barely passes, it usually is an indication of a bad crimp or bad connection at the RJ45 plug. Return loss is usually not significant in the loss of a signal, but rather signal jitter. Near-End Crosstalk (NEXT) In twisted-pair cabling Near-End Crosstalk (NEXT) is a measure that describes the effect caused by a signal from one wire pair coupling into another wire pair and interfering with the signal therein. It is the difference, expressed in dB, between the amplitude of a transmitted signal and the amplitude of the signal coupled into another cable pair, at the signal-source end of