Nortel Networks 1000 - Manual (Page 39)

Line cards 39
Table 3
Loop Start Call Processing A/B Bit Settings
Transmit Receive
State A B A B
Idle 0 1 0 1
Incoming Calls:
•
Idle 0 1 0 1
•
Ringing is applied from Lineside T1 card 0 1/0 0 1
•
Terminal equipment goes off-hook 0 1/0 1 1
•
Lineside T1 card stops ringing 0 1 1 1
Outgoing Calls:
•
Idle 0 1 0 1
•
Terminal equipment goes off-hook 0 1 1 1
Call Disconnect from far end:
•
Steady state (call in progress) 0 1 1 1
•
Far end disconnects by dropping loop current and Lineside T1
card changes Transmit A bit to 1 momentarily. 1 1 1 1
•
Terminal equipment responds causing Receive A bit to change
to 0. 1 1 0 1
•
Lineside T1 responds by changing its Transmit A bit to 0. Call is
terminated and set to idle state. 0 1 0 1
Call disconnect from terminal equipment:
•
Steady state (call in progress) 0 1 1 1
•
Terminal equipment goes on-hook causing the Receive A bit to
change to 0. Call is terminated and set to idle state. 0 1 0 1
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.
Nortel Communication Server 1000
Circuit Card Reference
NN43001-311 02.06 Standard
27 August 2008
Copyright © 2003-2008 Nortel Networks
.