Meridian America 71 ユーザーズマニュアル
ENGINEER TELEPHONE LINE
NOTES
Note:
This module is reissued change the minimum loop length requirement to
and to add metric equivalents.
(I) Cable pair selections must meet the following requirements:
l
AC signal loss must be
than 12.9
at 256
due to all sources
l
loop resistance must be less than 175 Ohm
l
Minimum loop length (mainframe bulkhead to telephone) of 30 m (100 ft)
l
Near end crosstalk coupling loss
at
frequency of 256
(not an issue for typical 22, 24, and 26 AWG twisted pair cable)
l
No bridge taps are permitted
l
No loading coils are permitted
Protection devices of the carbon-block and gas-filled type are permitted
if the off-state shunting impedance is better than 10
resistive,
and less than
capacitive.
(2) The following criteria have to be met where undercarpet cabling is used.
l
characteristic impedance at 256
10 Ohm
l
insertion loss at 256
4.6
l
next pair-to-pair coupling loss at 256
>
(3) For the typical system of 22, 24, or 26 AWG standard twisted pair cable,
the requirements translate to the following allowable loops.
the requirements translate to the following allowable loops.
. .
l
up to 915 m (3000 ft) of 22 or 24 AWG cable
l
up to 640 m (2100 ft) of 26 AWG cable
(4) If selected cable pair does not work satisfactorily. select another cable
pair using the following flowchart (Page 2):