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

Computer Networks and SecurityA broadband coax cable is similar in function and appearance tobaseband, although the cable is physically several times larger. BroadbandEthernet, in coax and optical fiber, will provide longer networksegments and increased channel capacity or channel transmission speed.It is called broadband since it provides a wider frequency range thanbaseband. There is multiple-channel broadband Ethernet cable, bothcopper and optical fiber. Various data transmission and encodingschemes are used in Ethernet. The broadband signal characteristics areshown in Table 7-3.Table 7-3. Broadband Signaling Characteristics————————————————————————————————Many channels on one cableSeparate frequency for each channelCarrier tone supplied by modemsModulation encoding schemesAM amplitude modulationFM frequency modulationPM phase modulationPCM pulse-code modulationPSK phase-shift keyingFSK frequency-shift keying————————————————————————————————Baseband cable includes 50-ohm Thicknet coaxial cable, 75-ohmThinnet and Cheapernet cable. The higher cable impedance of Thinnetand Cheapernet limits them to shorter segments because the signal degradesand attenuates with distances. The thinner cable is also moresusceptible to signal interference.Thinnet is a simple cable substitute for standard Ethernet networkcabling, while Cheapernet uses a different Ethernet controller-transceiverunit that is integrated in a single bus card or included on the PCmother board.Optical fiber cables are thinner, lighter and contain no metal. Theyare used to solve long-haul or security problems. Fiber can be used tointerconnect buildings miles apart.©2001 by The Fairmont Press, Inc. All rights reserved.