Meridian America 21 Manual De Usuario

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.

. .

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):