Section 150-231-134
Revision 01
Page 8
8. ALARM DESCRIPTION
8.01
The normally open alarm contacts available
across pins 20 & 21 comprise the HLU-231’s
Minor Alarm output. These alarm contacts close for
any of the following alarm conditions. Note that the
front panel message which accompanies each alarm
condition is shown in bold letters before each alarm
condition. Since more than one alarm condition can
exist at any given time but only one message can be
displayed, the alarms are listed in their order of
priorities. Only the highest priority alarm is displayed if
more than one alarm condition exists.
1) ALRM LOSW: Either HDSL loop loses sync.
2) ALRM LLOS: Loss of the HLU DS1 input signal.
3) ALRM RLOS: Loss of HRU DS1 input signal.
4) ALRM H1ES: HDSL Loop 1 has exceeded the 24
hour user-selected Errored-Seconds Cyclic
Redundancy Check (CRC) threshold.
5) ALRM H2ES: HDSL Loop 2 has exceeded the 24
hour user-selected Errored-Seconds CRC
threshold.
6) ALRM DS1: The total number of bipolar violations
(BPV) at the HLU and HRU T-1 input have
exceeded the 24-hour user-selected threshold.
7) ALM MAL1(2): The margin on HDSL Loop 1 or
Loop 2 has drooped below the minimum threshold
value set by the dumb terminal MARGIN ALARM
THRES; as described in Section 9.
8.02
The HLU 231’s STATUS LED flashes RED for
the duration of a minor alarm condition.
Alarms 4, 5 & 6 can be inhibited by selecting NONE
for the Errored Seconds Alarm (ESAL) system option.
See Section 9 for System Settings information. The
MAL(X) alarm can be disabled by setting the margin
alarm threshold to 0. The MNALRM can be retired by
executing the Alarm Cut Off (ACO) option. This is
accomplished by pressing the SEL button on the front
panel. This turns the alarm off and replaces the ALRM
message by the ACO message. The second part of
the ALRM message, which defines the cause of the
alarm, remains. Both messages remain until the alarm
condition clears or another alarm occurs.
8.03
Note that when both HDSL loops lose sync
word (LOSW), a minor alarm condition exists
but because the HLU enters a self test cycling mode,
the front panel LED lights yellow instead of red and
the SELF TEST message is displayed instead of the
ALRM message.
8.04
Setting the ALM option to DIS only prevents
the alarm relay from operating on a minor
alarm event. The STATUS LED still flashes red and
the ALRM message is still displayed. See paragraph
7.02.
8.05
Pin 32, FUSEALARM, is driven to -48 V and
the front panel STATUS LED turns red
whenever the on board fuse opens.
8.06
The HLU-231’s front panel tri-color STATUS
LED has the following states:
GREEN - Normal Operation
FLASHING GREEN - HDSL Acquisition
FLASHING RED - Minor Alarm (For conditions see
Paragraph 8.01)
RED - FUSEALRM
YELLOW - Self Test in process or an HLU loopback in
effect (CREM or NLOC).
FLASHING YELLOW - The HLU is in an ARMED
state.
