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Chapter 1: Product Description December 20, 2004
1-6 LTPH-UM-1261-01
Alarms Wire-Wrap Field
Terminate the alarm leads from the CO alarm system to the HMS-318 List 3 shelf. The Alarms wire-wrap field (TB2,
see Figure 1-2) is a 26-pin wire-wrap connector and provides a central connection point to the Normally Closed
(NC), Common (COM), and Normally Open (NO) relay contacts for installing optional alarm input connections (see
Table 1-1 on page 1-4 for Alarm descriptions). When an alarm is not active, there is continuity between the NC and
COM connections; when an alarm is active, there is continuity between the NO and COM connections.
Figure 1-4. Alarms Wire-Wrap Field (TB2)
Alarm Cutoff (ACO)
The Alarm Cutoff (ACO) function silences active audible alarms. Alarm cutoff can be achieved by pressing the ACO
button on the front panel of the Management Unit (for example, HMU-319) or by connecting the ACO pin 22 on the
HMS-318 List 3 shelf Alarms wire-wrap field (see Figure 1-4 on this page and Table 1-2) to ground through an
external NO push button switch. The ACO lead can be daisy-chained to other shelves for multi-shelf applications in
the same equipment rack.
!
IMPORTANT
Before making power connections (CO primary power feeds A and B) to the HMS-318 List 3 shelf,
ensure that the Main CO power breaker is off. Otherwise, severe injury to the installer or damage
to the unit may result.
Note: The NO and COM alarm relay connections can be daisy-chained between HMS-318 List 3 shelves
for multi-shelf applications in the same equipment rack.
NC C NO
CRIT AUD
CRIT VIS
MAJ AUD
MAJ VIS
MIN AUD
MIN VIS
SYS ID
ACO
123
4
5
6
7
89
10 11 12
13 14 15
16 17 18
19 20 21
22
0
6
-
1
2
6
1
R
1
ALARMS
23 24
GND
EXT
TEMP
25 26
NO COM
FAN