VeEX MPA, User Manual

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Term Definitions
797
Term Definitions
A B C D E F G H I J
K L M N O P Q R S T
U V W X Y Z
A
A1 and A2 bytes
Framing bytes. These two bytes indicate the beginning of the STM-N frame. The A1 and
A2 bytes are unscrambled. A1 has the binary value 11110110, and A2 has the binary
value 00101000. The frame alignment work of an STM-N frame is composed of (3 x N)
A1 bytes followed by (3 x N) A2 bytes.
AIS
Also known as a Blue Alarm . A signal that replaces the normal traffic signal when a
maintenance alarm indication has been activated. For SONET/SDH, AIS can occur due
to an LOS, LOF, or LOP failure on Line layer, Path layer, or Virtual Tributary.
AIS-L
Line Alarm Indication Signal. All-Ones pattern used to indicate if an alarm is being
received from upstream Line terminating equipment.
AIS-P
Path Alarm Indication Signal. Indicates if an alarm is being received from upstream Path
terminating equipment.
All Ones
Transmits a continuous test pattern of all ones (111111. . .). This pattern is generally
used to stress span repeater current regulator circuits. It can be used as an AIS in
unframed circuits, or a keep alive signal, idle code, or red alarm in other circuits.
All Zeros
MPA_e_manual_D07-00-129P_RevA00