Cabletron Systems SEHI-22 User Manual

Also see for SEHI-22: User guide Addendum

Contents

CHAPTER 2: INSTALLATION REQUIREMENTS/SPECIFICATIONS2-2SEHI USER’S GUIDE2.1.2 UTP and STP Cable SpecificationsThe device at the other end of the twisted pair segment must meet IEEE802.3 10BASE-T specifications. When connecting a 10BASE-T TwistedPair Segment to the SEHI 10BASE-T Twisted Pair Network Ports andEPIM-T module, the network must meet the following requirements:LengthThe IEEE 802.3 10BASE-T standard requires that 10BASE-T devicestransmit over a 100 meter (328 foot) link using 22-24 AWG unshieldedtwisted pair wire. However, cable quality largely determines themaximum link length. With high quality, low attenuation cable, linklengths of up to 200 meters are achievable. Cable delay limits themaximum link length to 200 meters, regardless of the cable type.Insertion LossThe maximum insertion loss allowed for a 10BASE-T link is 11.5 dB atall frequencies between 5.0 and 10 MHz. This includes the attenuation ofthe cables, connectors, patch panels, and reflection losses due toimpedance mismatches in the link segment.ImpedanceCabletron Systems 10BASE-T Twisted Pair products work on twisted paircable with 75 to 165 ohms impedance. Unshielded twisted pair cablestypically have an impedance of between 85 to 110 ohms.Shielded twisted pair cables, such as IBM Type 1 cable, are also used. Theimpedance of IBM Type 1 cable is typically 150 ohms. Higher impedanceIBM Type 1 cable increases signal reflection, but because the cable isshielded, signal reflection has little effect on the received signal’s qualitydue to the lack of crosstalk between the shielded cable pairs.JitterIntersymbol interference and reflections cause jitter in the bit cell timing,resulting in data errors. A 10BASE-T link must not generate more than5.0 ns of jitter. If the cable meets the impedance requirements for a10BASE-T link, jitter should not be a concern.