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364 CHAPTER 10: TROUBLESHOOTING
Alarm Descriptions Red Alarm
■ Carrier Fail Alarm (Red CFA) — A state that exists at a downstream
terminal device, based upon the terminal device detecting an
incoming LOS or LOF.
Blue Alarms
■ AIS, Keep-alive/Blue — A signal that is transmitted instead of the
normal signal to maintain transmission continuity and to indicate to
the receiving equipment that there is a transmission interruption either
at the equipment that is generating the AIS signal or upstream of that
equipment. The all ones signal is generated:
■ To maintain transmission continuity
■ To notify downstream equipment of a transmission fault
■ To indicate to downstream equipment that a DS1 framed signal is
not being generated
The transmission fault may be located at the equipment that is
generating the alarm signal, or it may be located upstream of that
equipment.
■ AIS CFA (also known as Blue CFA) — A state that exists at the
downstream equipment and indicates that it has detected an AIS
signal from the upstream equipment.
Yellow Alarms
■ RAI (also known as Yellow Alarm Signal) — A signal transmitted in
the outgoing direction when a terminal determines that it has lost the
incoming signal. The terminal equipment generates the Yellow Alarm
Signal for a minimum of 1 second using one of these methods:
■ If you are using Super Frame (SF), the terminal equipment
generates the Yellow Alarm Signal by setting the second bit in all
channels of the Super Frame to 0 (zero).
■ If you are using Extended Super Frame (ESF), the terminal
equipment generates the Yellow Alarm Signal by sending an
alternating pattern of 8 ones followed by 8 zeros on the Facilities
Data Link (FDL).
■ Yellow CFA — A state that is activated at the terminal equipment
when the terminal equipment detects a Yellow Alarm Signal. The
Yellow Alarm Signal comes from the equipment at the other end