Chapter 1.Understanding ISDN and the ISU 2x644 ISU 2x64 Dual Port ISDN Service Unit User Manual 61200051L1-1DFigure 1-2ISU 2x64 Front PanelISU 2X64 INTEROPERABILITYTelephone networks are evolving from analog technologies todigital technologies such as ISDN. This transition is time-consum-ing and costly for the telephone companies and upgrading all lo-cations and facilities is a lengthy process.The ISU 2x64 bridges this transition by supporting communica-tions with existing and future network services and equipment.The ISU 2x64 supports communications with Switched 56 Serviceand Switched 56 DSUs (2-wire and 4-wire) as well as variousISDN terminal adapters, ISDN terminal equipment, and BOND-ING-compatible Inverse Multiplexers.Figure 1-3 illustrates the ISU 2x64 operation in various switchednetwork services and customer premises products.ISU 2X64 SINGLE PORT OPERATIONThe ADTRAN ISU 2x64 is designed to operate over multipointISDN lines in North America that will require two Service ProfileIdentification (SPID) numbers from the telephone company whenthe ISDN lines are installed. These SPID numbers tell the ADT-RAN ISU 2x64 which port or DTE# to route incoming and outgo-ing calls. See Ordering ISDN Without IOCs on page 125 for furtherdetails on ordering multipoint ISDN service.ENTER 1 2 34 5 67 8 9#0*CANCELRS CS TD RD CD TR SRISU 2X64
