Unit installation

Appendix C Operating Environment Installation and Operation Manual
C-4 E1 Environment FCD-E1
E1 (CEPT) Line Alarm Conditions
• Excessive bit error rate. The bit error rate is measured on the frame alignment
signal. The alarm threshold is an error rate higher than 10
-3
that persists for 4
to 5 seconds. The alarm condition is canceled when the error rate decreases
below 10
-4
for 4 to 5 consecutive seconds.
• Loss of frame alignment (also called loss of synchronization). This condition is
declared when too many errors are detected in the frame alignment signal
(FAS), e.g., when 3 or 4 FAS errors are detected in the last 5 frames. Loss of
frame alignment is cleared after no FAS errors are detected in two consecutive
frames. The loss of frame alignment is reported by means of the A bit (see
Figure C-1).
• Loss of multiframe alignment (applicable only when 256S multiframes are
used). This condition is declared when too many errors are detected in the
multiframe alignment signal (MAS), as for loss of frame alignment. The loss of
multiframe alignment is reported by means of the Y bit (see Figure C-1).
• Alarm indication signal (AIS). The AIS signal is an unframed “all-ones” signal,
and is used to maintain line signal synchronization in case of loss of input
signal, e.g., because an alarm condition occurred in the equipment that
supplies the line signal. Note that the equipment receiving an AIS signal loses
frame synchronization.