For T1 links, the Loss Of Frame failure is declared when an OOF or LOS 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 TR 62411 [16]. For E1 links, the Loss Of Frame Failure is declared when an OOF defect is detected.