Nortel NT1R20 Description page 70

Page 46 of 290 Description
553-3001-105 Standard 5.00 June 1999
Call disconnect from line-side T1 terminal equipment
while a call is in process, the terminal equipment may disconnect by going
on-hook, causing the line-side T1's receive A bit to change to 0. The line-side
T1 card responds to this message by simulating the removal of ground from
the tip by changing its transmit A bit to 1. The call is now terminated and the
interface is once again in the idle condition.
Table 5 outlines the line-side T1's A and B bit settings in each state of call
processing.
Ground Start Restrictions
If you are using the line-side T1 card in ground start mode, certain restrictions
should be considered. Because the Meridian 1 system treats the line-side T1
card as a standard loop start analog line card, the ground start operation of the
line-side T1 card has operational limitations compared to typical ground start
interface equipment relating to start of dialing, distant end disconnect and
glare potential.
Distant end disconnect restrictions
feature is not available in your Meridian 1 software, the line-side T1 card is
not capable of indicating to the CPE equipment when a call has been
terminated by the distant end. In this case, the line-side T1 card will continue
to provide a grounded tip indication (A=0) to the CPE equipment until it
detects an open loop indication (A=0) from the CPE, at which time it will
provide an open tip indication (A=1). Therefore, without SAL software, the
line-side T1 card is not capable of initiating the termination of a call to the
CPE equipment.
Since the X11 software releases 21 and later support the SAL feature, with
these software releases this restriction does not exist. With the SAL software
configured for each line-side T1 line, the line-side T1 card will provide an
open tip indication to the CPE equipment when it receives an indication of
supervised analog line from the Meridian 1 system, thus providing normal
ground start protocol call termination.
Alternatively,
If the supervised analog line (SAL)