Nortel Networks Circuit Card User Manual

 Overview

The digital pad for lineside T1 card audio level is fixed for all types of call 
connection (0 dB insertion loss in both directions), and differs from the 
analog line. Audio level adjustments, if required, must be made in the lineside 
T1 terminal equipment.

Off-premise applications are installations where the telephone lines are 
extended outside the building where the PBX system is housed, but the lines 
are not connected to public access facilities. This application is commonly 
referred to as a “campus installation.”

In off-premise applications, special protection devices and grounding are 
required to protect PBX and telephone components from any abnormal 
conditions, such as lightning strikes and power line crosses. 

The NT1R20 Off-Premise Station Line card has built-in protection against 
lightning strikes and power line crosses. These should be the preferred cards 
for an off-premise application. Other cards can be used when external line 
protectors are installed.

When using the lineside T1 card for an off-premise or network application, 
external line protectors must be installed. Install an isolated type Channel 
Service Unit (CSU) as part of the terminal equipment, to provide the 
necessary isolation and outside line protection. The CSU should be an FCC 
part 68 or CSA certified unit.

Line protectors are voltage-absorbing devices that are installed at the 
cross-connect terminals at both the main building and the remote building. 
The use of line protectors will ensure that system and telephone components 
are not damaged from accidental voltages that are within the limit of the 
capacity of the protection device. Absolute protection from lightning strikes 
and other stray voltages cannot be guaranteed, but the use of line protection 
devices significantly reduces the possibility of damage.