Data Communications Networking Devices - 4th Ed.pdf

60 _______________________________ FUNDAMENTAL WIDE AREA NETWORKING CONCEPTSTable 1.19 ANSI X3S3 data communications technicalcommittee task groupsTask groupResponsibilityX3S31PlanningX3S32GlossaryX3S33Transmission formatX3S34Control proceduresX3S35System performanceX3S36Signaling speedsX3S37Public data networksstandards committee has grown to 25 technical committees to include the X3S3Data Communications Technical Committee which is composed of seven taskgroups. Table 1.19 lists the current task groups of the ANSI X3S3 Data CommunicationsTechnical Committee and their responsibilities.Foremost among ANSI standards are X3.4 which de®nes the ASCII code andX3.1 which de®nes data signaling rates for synchronous data transmission on theswitched telephone network.Table 1.20 lists representative ANSI data communications standards publicationsby number and title. Many of these standards have been adopted by the USgovernment as Federal Information Processing Standards FIPS). The reader isreferred to Table 1.23 at the end of this section for a list of the addresses ofstandards organizations mentioned in this section.EIAThe Electronic Industries Association EIA) is a trade organization headquarteredin Washington,DC,which represents most major US electronics industrymanufacturers. Since its founding in 1924,the EIA Engineering Department haspublished over 500 documents related to standards.In the area of communications,the EIA established its Technical CommitteeTR-30 in 1962. The primary emphasis of this committee is upon the developmentand maintenance of interface standards governing the attachment of data terminalequipment DTE),such as terminals and computer ports,to data communicationsequipment DCE),such as modems and digital service units.TR-30 committee standards activities include the development of theubiquitous RS-232 interface standard which describes the operation of a 25-pinconductor which is the most commonly used physical interface for connectingDTE to DCE.Two other commonly known EIA standards and one emerging standard are RS-366A,RS-449,and RS-530. RS-366 describes the interface used to connectterminal devices to automatic calling units; RS-449 was originally intended toreplace the RS-232 interface due to its ability to extend the cabling distancebetween devices,while RS-530 may eventually evolve as a replacement for bothRS-232 and RS-449 as it eliminates many objections to RS-449 that inhibited its