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ALM
(Alarm) glows red to indicate that one of
several alarm conditions exist. These con-
ditions may be local alarms or remote alarm
conditions. Alarms may occur due to:
• Loss of Synchronization
• Loss of Frame
• AIS (Blue Alarm)
• Yellow Alarm
ERR
(Error) flashes to indicate errors. There are
several flashing patterns to indicate the type
of error.
Invalid Switch Configuration: It is possible
to request more bandwidth than is possible.
For instance, if you set the starting channel
to 12, and you select a number of timeslots
exceeding 13, the unit will not be able to
satisfy your request. In that case, the ERR
LED will flash once a second (fi second on,
fi second off). When the unit detects an
invalid setting, it will ignore the setting and
default to a full T1 (bandwidth = 24 chan-
nels, starting channel = 1). This will contin-
ue until you set the switches to a valid set-
ting. The invalid switch configuration condi-
tion overrides other error conditions. Thus, if
• Errored Second: In ESF or SF framing, if
the unit detects a frame error, the ERR LED
will flash briefly once a second.
• Framing Mismatch: the ERR LED flashes
briefly once a second when framing modes
are mismatched.
• Loss of Signal: When there is no signal
at the network interface, the ERR LED will
flash briefly once a second.
TST
(Test/Loop) glows yellow to indicate that the
unit is in a test mode. The unit may be in
any one of the following modes:
• D4 Line Loop (CO initiated)
• ESF Line Loop (CO Initiated)
• ESF Payload Loop (CO Initiated)
PWR
(Power) glows green to indicate that the unit
is receiving power.
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5.2 CENTRAL OFFICE LOOPS
The 2711 also responds to central office initiated loop commands.
When in D4 framing mode, the 2711 will implement the “loop up” com-
mand when it recognizes the pattern “10000” in the data stream for a
minimum of 5 seconds. The “loop down” command is implemented by
the pattern “100” in the data stream for a minimum of 5 seconds.
When operating in ESF framing mode, loopback commands are
issued via the Facility Data Link (FDL). The line loop message will
cause a loop back before data enters the framer portion of the CSU.
The payload loop message will cause the 2711 to loop data after the
framer portion of the CSU.
The 2711 will respond to Universal Loopback Deactivate to clear
all central office loops.
