Voice Frequency Audio Level; Off-Premise Line Protection - Avaya Nortel Communication Server 1000 Reference

With the SAL software configured for each Lineside T1 line, the Lineside T1 card provides an
open tip indication to the CPE when it receives an indication of supervised analog line from
the system. This provides normal ground start protocol call termination.
Glare restrictions
In telephone lines or trunks, glare occurs when a call origination attempt results in the
answering of a terminating call that is being presented by the far end simultaneously with the
call origination attempt by the near end.
The Lineside T1 detects presentation of a terminating call (outgoing to Lineside T1 terminal
equipment) by detecting ringing voltage. If application of the ringing voltage is delayed due to
traffic volume and ringing generator capacity overload, the Lineside T1 ground start operation
cannot connect the tip side to ground to indicate the line is seized by the system.
In ground start mode, glare conditions need to be considered if both incoming and outgoing
calls to the Customer Premise Equipment (CPE) are going to be encountered. If the system
and the CPE simultaneously attempt to use a Lineside T1 line, the system completes the call
termination. It does not back down and allow the CPE to complete the call origination, as in
normal ground start operation.
If both incoming and outgoing calls are to be handled through the Lineside T1 interface,
separate channels should be configured in the system and the CPE for each call direction.
This eliminates the possibility of glare conditions on call origination.

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.
Circuit Card Reference
Line cards
July 2011 55