ISND SYSTEM HAVING SUSBCRIBER LINE MULTIPLEXER WITH MEANS FOR ESTABLISHING DIFFERENT DATA LINKS THROUGH D-CHANNELS ON SUBSCRIBER LINE AND HIGH RATE TRANSMISSION LINE

摘要

42 In an ISDN system comprising a plurality of DSLs each having a plurality of DTEs and an ISDN switch having a TEI list, a multiplexer is used for enabling each DTE to access the ISDN switch through a single primary rate DTL in the time division technique. The multiplexer comprises subscriber interfaces connected to DSLs, repectively. The subscriber interface has first TEIs assigned to DTEs on the corresponding DSL and has a first data link with each DTE on the basic interface D channel using a first LAPD frame signal with the fisrt TEIs. The subscriber interface has a second TEI assigned thereto and registered in the TEI list in the ISDN switch. The subscriber interface derives information field from the first LAPD signal and forms a second LADP frame signal having the second TEI and the derived information, The multiplexer statisticaly multiplexes a plurality of second LAPD signals from subscriber interfaces into the D channel on the DTL to form a second data link between each subscriber interface and the ISDN switch so that load of the ISDN switch is reduced. Addition of a switch selection code to the second TEI enables to switch the multiplexer to another ISDN by use of a cross-connector on the DTL. Use of line selecting signal in DTE signal also enables the multiplexer to transmit the DTE signals onto a different private line.