Interphase Tech RAS Communications Controller 5536 - Manual (Page 193)

Appendix E: Line Status Utility
5536 PRI RAS Communications Controller Users Guide 173
Alarm LEDs
The following alarm LEDs indicate connection problems that
result from line failures:
LED Meaning
LOS Loss of Signal. Typically appears when no electrical signal is
detected. (Check if the line is plugged in on the board and on the
network interface).
LOF Loss of Frame (also known as Red Alarm). Appears when many
frames are lost because of framing errors. The terminal is unable
to synchronize on the DS1 signal.
AIS Alarm Indication Signal (also known as Blue Alarm).
Transmitted instead of the normal signal to maintain
transmission continuity. Also indicates to the receiving
equipment that a transmission interruption occurred either at the
equipment originating the AIS signal, or upstream of the
originating equipment.
RAI Remote Alarm Indication (also known as Yellow Alarm).
Transmitted in the outgoing direction when a terminal
determines that it has lost the incoming signal.