This counter reports the cumulative time this T1 interface has spent receiving a 'blue alarm,' an unframed, all-ones signal, since system startup. A blue alarm typically means the far-end equipment has itself lost its input signal and is sending an idle/alarm indication, so admins use this counter to trace outages back toward the upstream carrier rather than the local card. A rising dsx1ExtCfgT1RxBlueAlarm value while the local port shows no cabling fault points the admin to check the far-end T1 equipment or carrier circuit.