Leased Line DTE Migration to ISDN Switched Network
Original Publication Date: 1989-Mar-01
Included in the Prior Art Database: 2005-Jan-27
Disclosed are new leased-line Data Terminal Equipment (DTE) interfaces allowing secure leased-line operation on Integrated Services Digital Network (ISDN) switched networks. The introduction of ISDN leads to the design of Terminal Adapters which will insure migration of existing DTEs towards ISDN. Among those DTEs are X.21 bis leased interface DTEs and X.21 leased interface DTEs. Until now, DTEs designed for leased-line operation assume that unless some failure has occurred on the leased line, the line is available and the DCEs attaching to the leased line are powered ON and ready (data set ready (DSR) 107 is ON at the X.21 bis interface). If the link is not available anymore, failure of the line or outage of the DCEs, the interface will indicate Data Set Not Ready and the DTE terminates the session(s) on that line.