Section 150-431-114
Release 01
Page 37
18.02
The maximum HLU-431, List 1D power
dissipation is the power that is converted into heat
within the unit. It contributes to the total heat generated
and is used to determine the maximum number of shelves
per bay that do not exceed the maximum power dissipation
density in Watts/ sq. ft.
18.03
In CO locations, the maximum power dissipation
for open-faced, natural convection cooled
mountings is 120 Watts/sq. ft., as stated in NEBS standard
TR-NWT-000063 Section 4.2.3. The footprint of a 14-
slot, 23" wide shelf with 400 mechanics is 7,004 sq. ft..
Thus the maximum allowable dissipation is 840 W. This
limits the number of HLU-431, List 1D units per bay to 93
when powering the HDU-451, List 1 and List 2 or the
HDU-439/437, List 1 Doubler, and 98 when powering the
List 3 or List 4 doubler.
Note that this is a worst case situation since it assumes the
entire CO is subjected to the maximum power density.
More favorable conditions would permit increasing the
number of shelves per bay without jeopardizing the CO
thermal integrity.
18.04
The thermal loading limitations imposed when
using the HLU-431, List 1D in a Controlled
Environmental Vaults (CEV) or other enclosures are
determined by applying the HLU-431, List 1D power
parameters to the manufacturer requirements for each
specific housing.
18.05
The power consumption listed in Table 11 is the
total power that the HLU-431, List 1D consumes
or draws from its -48 VDC shelf power source. This
parameter is needed when the HLU-431, List 1D is located
remote to its serving CO. It determines the battery
capacity required to maintain an 8-hour stand-by battery
reserve for emergency situations. It thus limits the
maximum number of plugs per remote enclosure. Use this
data to perform this analysis on a case by case basis.
18.06
Heat baffles should be placed between every
other shelf, in racks containing more than two
shelves. This technique deflects the rack heat outward and
reduces thermo stress on the plugs.
19. LOOPBACK OPERATION
19.01
The HiGain system has a family of loopback
options. The most important of these is the
Smart-Jack loopback which enables the HRU-412 to
respond to the standard (2/3 in 5) Smart-Jack in-band
loopback codes. This option can be ENAbled or DISabled
from either the front panel settings or the terminal System
Settings Menu screen.
19.02
In addition to the Smart-Jack loopback, the
HiGain system can be configured for one of five
special in-band loopback (SPLB) command sequences.
These are selected from the SPLB user options shown in
Table 1. The loopback locations are shown in Figure 15.
19.03
“GNLB” is the HiGain system Generic Loopback
code. The GNLB allows in-band codes from the
network to loop up either the HLU/NLOC (4 in 7) or the
HRU/ NREM (3 in 7) toward the network. In addition, it
allows in-band codes from the Network Interface (NI) to
loop up the HLU/CREM (6 in 7) or the HRU/CLOC (5 in
7) toward the customer. For doubler applications, it
permits looping doubler number 1 toward the network
NDU1 (2 in 6) or toward the customer CDU1 (4 in 6).
Doubler number 2 is looped toward the network with
NDU2 (3 in 6) or toward the customer with CDU2 (5 in 6).
Either loop-up condition is terminated (looped down) with
the (3 in 5) loop-down code. All messages must be present
for five seconds before the HiGain system will respond.
Table 12 lists the test procedures that apply when using the
GNLB mode.
19.04
The A1LB loopback selection complies with that
proposed for HDSL systems in the T1/E-1.4/92
recommendation with the following additions (see Table
13):
•
Query loopback
•
IOR power-down
•
Three loopback time-out choices
•
Initiation from either end
•
Repeating bit error signatures
•
Alternate query loopback.
These additions make A1LB identical to the A2LB, but
they retain separate identities to allow future T1/E1
enhancements to A1LB without affecting A2LB.
