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Line cards 39
Transmit Receive
State A B A B
•
Idle
0101
•
Ringing is applied from Lineside T1 card
0
1/0
01
•
Terminal equipment goes off-hook
0
1/0
11
•
Lineside T1 card stops ringing
0111
Outgoing Calls:
•
Idle
0101
•
Terminal equipment goes off-hook
0111
Call Disconnect from far end:
•
Steady state (call in progress)
0111
•
Far end disconnects by dropping loop current and Lineside T1
card changes Transmit A bit to 1 momentarily.
1111
• Terminal equipment responds causing Receive A bit to change
to 0.
1101
• Lineside T1 responds by changing its Transmit A bit to 0. Call is
terminated and set to idle state.
0101
Call disconnect from terminal equipment:
•
Steady state (call in progress)
0111
•
Terminal equipment goes on-hook causing the Receive A bit to
change to 0. Call is terminated and set to idle state.
0101
Ground Start Mode
In Ground Start mode, the A and B bits meaning is:
•
Transmit from LTI:A bit = Tip ground (0=grounded, 1=not grounded); B
bit = Ringing (0=on, 1=off)
•
Receive to LTI: A bit = Loop (0=open, 1=closed); B bit = Ring ground
(0=grounded, 1=not grounded)
When a T1 channel is idle, the Lineside T1 card simulates a ground on the
tip lead and -48V dc on the ring lead to the terminal equipment by setting
the transmit A bit to 1 and transmit B bit to 1. Accordingly, an on-hook
telephone simulates an open loop toward the Lineside T1 card, causing the
Lineside T1 card’s receive bits to be set to A = 0 and B = 1.
Incoming Calls Incoming calls to terminal equipment that is connected to
the Lineside T1 card can originate either from stations that are local (served
by the PBX), or remote (served through the public switched telephone
network). To provide the ringing signal to the terminal equipment the
Lineside T1 card simulates the 90V ring signal on the ring lead by alternating
Nortel Communication Server 1000
Circuit Card Reference
NN43001-311 01.04 Standard
Release 5.0 23 May 2008
Copyright © 2003-2008, Nortel Networks
.