Verilink AS2000: The Basics (880-502981-001) Product Manual - Manual (Page 172)

Acronyms and Definitions
Glossary-52 Verilink Access System 2000: Basics
Y
yellow alarm A T1 alarm signal sent back toward
the source of a failed transmission
in a DS1 transmission path. Also
known as remote alarm indication
signal (RAI). Yellow alarms are
transmitted by a Channel Service
Unit (CSU) or DSX-1 device which
is in a red alarm condition such as
loss of signal (LOS) , loss of
frame (LOF) , or received alarm
indication signal (AIS) .
yellow alarm transcoding When a T1 signal undergoes
framing format conversion from
Superframe (SF/D4) to
Extended Superframe Format
(ESF) , or ESF to SF, an existing
yellow alarm is transcoded to the
new format, and the alarm can be
detected by the network or data
terminal equipment (DTE)
equipment. An integration time is
used before transcoding occurs so
data that looks like a yellow alarm
(in the SF mode), and to allow for
detection of a yellow alarm in the
presence of errors. For SF, the
detection and clear time is 400 ± 1
millisecond. For ESF, this time is
63 to 66 milliseconds.