Nortel Circuit Card, Installation Manual, Page: 57 / 908

Overview Page 57 of 906
Circuit Card Description and Installation
Voice frequency audio level
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 line protection
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
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.