29406

ISDN Layer 2 has told ISDN Layer 3 that it is not possible to send Layer 3 messages to the switch. If the timer T309 is enabled (see ISDN signalling section of the System Configuration menu option), all calls are cleared except active calls until the timer times out (after 120 seconds), or the link is activated again. If T309 is disabled, all calls are cleared. If the system is T1/uLaw and NFAS is being used with a backup D channel, the Layer 3 process may automatically switch the primary data link to the backup data link on a different trunk. Active calls are preserved, but all other calls are cleared.