This writable value configures, in seconds, ATM signaling timer T303, which starts when a SETUP message is sent in the Call Present state; it is stopped by ALERT, CONNECT, RELEASE COMPLETE, or CALL PROCEEDING, and on first expiry the SETUP is resent and the timer restarted, while a second expiry clears the connection and returns to the NULL state. It lets an admin tune how aggressively the switch retries a call setup attempt that isn't getting an initial response. For example, shortening T303 on a low-latency link would make the switch retry an unanswered SETUP sooner rather than waiting the full default interval.