Cable Tests
Introduction 4
Twisted pair cable is currently the most popular cable in LAN systems. The
UTP cable typically consists of four pairs of 24 AWG (American Wire Gauge) solid or stranded wire surrounded by an insulating jacket. ScTP cable adds a foil shield around the four pairs to improve its noise immunity. The wires in each pair are twisted around each other, and the four pairs, in turn, are twisted together inside the cable sheath. Most UTP and ScTP cables have characteristic impedance of 100Ω. However, in some countries UTP is also available in 120Ω. The Cable Tests described in this chapter are designed to work with 100Ω cabling systems.