HVAC Control in the New Millennium.pdf - HVAC.Amickracing

Computer Networks and SecurityThinnet and Cheapernet cables have similar compositions. Thedielectric is a type of foam and the exterior insulating jacket can bepolyvinyl chloride (PVC) or the more expensive, fire-resistant fluorinatedethylene propylene (FEP) Teflon for installation in building plenumsand walls.Baseband Ethernet can run on twisted-pair telephone wiring. Thistype of cable has bundles of wires containing 4, 6, or 8 wiring pairswhich are twisted around each other. The wires are twisted to minimizecrosstalk, signal attenuation and susceptibility to stray noise (See Tables7-4, 7-5).Table 7-4. Ethernet Baseband Variants————————————————————————————————Specifications Ethernet Cheapernet Thinnet Twisted-PairSegment length (m) 500 200 200 250Transceiversper segment 100 100 100 512Maximum numberof segments 3 3 3 3Network length (m) 1500 600 600 500————————————————————————————————Table 7-5. Baseband Signaling Characteristics————————————————————————————————One channel per coaxial cableNo carrierDC to upper frequency limitEncoding schemesManchesterReturn-to-zeroNon-return-to-zeroDigital transmission, no modem translation————————————————————————————————Ethernet CompatibilityNetwork compatibility is a function of network length and lengthof individual node connections. Ethernet transmission is based upon a©2001 by The Fairmont Press, Inc. All rights reserved.