Nortel DMS-100 Series Maintenance Manual page 125

Frame current with line drawers supplied
Drawers
6
7
8
9
10
Current demands with the line off-hook
The amount of current that an off-hook line draws depends on the length of
the loop.
For these calculations, model an NT6X17AA line card has the following
parameters:
line card battery feed resistance is 440 Ω
phone resistance is 200 Ω
assumed short loop resistance is 50 Ω
assumed average loop resistance is 800 Ω
Use these values to estimate the off-hook line power requirements. The
off-hook current for short loop is 77 mA and off-hook current for average
loop is 77 mA.
Determine the estimated percentage of installed lines that are off-hook.
Assume a call rate of 3.0 CCS or about 8.3% of the installed lines off-hook.
For the OPAC, 8.3% of the lines is 54.
To calculate the total OPAC power demand, use the following equation:
(Number of lines off-hook) x (current per line) + base PWR demand +
additional equipment current draw = Total frame power demand.
An OPAC with 640 lines, with 54 lines off-hook and 50 Ω loops has the
following power demand:
base frame current with 10 line drawers is 16.16 A
total off-hook line current = (54 lines) x (77 mA/line) is 4.16 A
DMS-100 Family OPAC Maintenance Manual XPM12 and up
OPAC maintenance overview 2-31
(continued)
Line cards
384
448
512
576
640
—end—
Frame current demand
(A)
14.64
15.02
15.4
15.78
16.16