Nortel Networks Circuit Card 311 - Manual (Page 41)

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.
Table 4 "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.
Table 4
Ground Start Call Processing A/B Bit Settings
Transmit Receive
State A B A B
Idle 1 1 0 1
Incoming Calls (to terminal equipment):
• Idle 1 1 0 1
• Ringing is applied from Lineside T1 card by simulating ground on
tip lead and ringing on ring lead. 0 0/1 0 1
• Terminal equipment goes off-hook by simulating ground on tip
lead and ringing on ring lead. 0 0/1 1 1
Outgoing Calls (from terminal equipment):
• Idle 1 1 0 1
• Terminal equipment goes off-hook. 1 1 0 0
• The Lineside T1 simulates grounding its tip lead 0 1 0 0
• Terminal equipment opens ring ground and closes loop 0 1 1 1
Call Disconnect from far end:
• Steady state (call in progress) 0 1 1 1
• The Lineside T1 ungrounds tip 1 1 1 1
• Terminal equipment opens loop current 1 1 0 1
Call disconnect from terminal equipment:
• Steady state (call in progress) 0 1 1 1
• Terminal equipment goes open loop current 0 1 0 1
• Lineside T1 card opens tip ground 1 1 0 1
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 23 May 2008
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