Quatech Asynchronous Communications Adapter QSCLP-100 User Manual

Also see for QSC(LP)-100: Specifications User manual

Quatech Asynchronous Communications Adapter QSCLP-100 User Manual Manual pdf 31 page image

7 External ConnectionsRS-232-C devices are classified by their function as either Data TerminalEquipment (DTE) or Data Communication Equipment (DCE). Generally, dataterminal equipment is defined as the communication source and datacommunication equipment is defined as the device that provides a communicationchannel between two DTE-type devices.TelephonelineDCEDCEDTEDTE RS-232-CRS-232-CModemModemTerminalTerminalFigure 16 --- Use of DTEs and DCEs in a communications linkDTE- and DCE-type devices have complementary pinouts to allowterminals and modems to be connected directly using a one-to-one cable as shownin Figure 16. In many applications, DCEs are unnecessary, and in these cases acable called a "null modem cable" or "modem eliminator cable" is used to directlyconnect two DTE-type devices. A typical null modem cable is also shown inFigure 17.RxDTxDRTSCTSDTRDSRDCDGND(3)(2)(4)(5)(20)(6)(8)(22)(7)RITxDRxDCTSRTSDSRDTRDCDGND(3)(2)(4)(5)(20)(6)(8)(22)(7)RIRxDTxDRTSCTSDTRDSRDCDGND(3)(2)(4)(5)(20)(6)(8)(22)(7)RIDCDGND(8)(22)(7)Typical DTE-to-DCE cableRIDCDGNDRxDTxDRTSCTSDTRDSR(3)(2)(4)(5)(20)(6)(8)(22)(7)RIDCDGND(8)(22)(7)RxDTxDRTSCTSDTRDSR(3)(2)(4)(5)(20)(6)Typical DTE-to-DTE null modem cableFigure 17 --- Cabling requirements for RS-232-C devices(cables using 25-pin connectors shown)QSC(LP)-100 User's Manual 31