System interfaces
38
System functions and features as of R3.0
syd-0367/1.3 – R3.0 – 03.2013
2. 1. 4. 2
Attenuation on analogue network interfaces
With analogue network connections you have a choice of four different attenua-
tion settings:
•
Long
or.
•
Long D
for long lines
•
Short
or
•
Short D
for short lines
On lines with a loop resistance < 280
Ω
,
Short
or
Short D
should be selected to
avoid problems with echo or instability (feedback).
The "
… D
" settings are used to increase the volume in an "analogue exchange - dig-
ital terminal" connection type by 3 dB in both directions as this type of connection
is generally perceived as too quiet. The reference level is modified accordingly on
the expansion card. Due to the restriction to the aforementioned call type the "
…
D
" setting does not result in an increase if an analogue terminal interface is in-
volved in a connection.
Note:
"
… D
" setting should not be used (or only once the stability conditions
have been thoroughly clarified) if the equipment (Terminal Adapter)
operated on digital interfaces also features a four-wire to two-wire con-
version, i. e. an analogue two-wire interface.
Default setting
Analogue network interfaces are set on
Long D
.
