This trap indicates that the specified DS1 channel is experiencing a Loss Of Frame (LOF) failure. A LOF is also referred as a Red alarm signal. LOF is declared when an OOF (Out of Frame) or LOS (Loss of Signal) defect has persisted for T seconds, where 2 <= T <= 10. The Loss Of Frame failure is cleared when there have been no OOF or LOS defects during a period T where 0 <= T <= 20. Many systems will perform 'hit integration' within the period T before declaring or clearing the failure (e.g., see AT&T Technical Reference TR 62411 ACCUNET T1.5).