Line cards 41
Call disconnect from Lineside T1 terminal equipment Alternatively,
while a call is in process, the terminal equipment may disconnect by going
on-hook, causing the lineside T1’s receive A bit to change to 0. The Lineside
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.
Table4 "Ground Start Call Processing A/B Bit Settings" (page 41) outlines
the lineside T1’s A and B bit settings in each state of call processing.
Tabl e 4
Ground Start Call Processing A/B Bit Settings
Transmit Receive
State A B A B
Idle 1101
Incoming Calls (to terminal equipment):
•Idle 1101
•Ringing is applied from Lineside T1 card by simulating ground on
tip lead and ringing on ring lead. 00/1 01
•Terminal equipment goes off-hook by simulating ground on tip
lead and ringing on ring lead. 00/1 11
Outgoing Calls (from terminal equipment):
•Idle 1101
•Terminal equipment goes off-hook. 1100
•The Lineside T1 simulates grounding its tip lead 0100
•Terminal equipment opens ring ground and closes loop 0111
Call Disconnect from far end:
•Steady state (call in progress) 0111
•The Lineside T1 ungrounds tip 1111
•Terminal equipment opens loop current 1101
Call disconnect from terminal equipment:
•Steady state (call in progress) 0111
•Terminal equipment goes open loop current 0101
•Lineside T1 card opens tip ground 1101
Ground Start Restrictions
If the Lineside T1 card is used in ground start mode, certain restrictions
should be considered. Because the system treats the Lineside T1 card as
a standard loop start analog line card, the ground start operation of the
Nortel Communication Server 1000
Circuit Card Reference
NN43001-311 01.04 Standard
Release 5.0 23May 2008
Copyright© 2003-2008, Nor tel Networks
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