Nortel Circuit Card Installation Manual page 586

Page 586 of 906
Figure 124
DID trunk, loop DR call connection sequence – incoming call from CO
A
Near end
System
State
Idle
Trunk seizure
Outpulsing
A rings
2-way voice
connection
B goes on hook
Idle
A goes on hook
Idle
553-3001-211 Standard 3.00
NT8D14 Universal Trunk card
Signal/direction
Ground
on tip/
battery
resistance
on ring
Low-resistance loop
Address signaling
Ringback
Battery on tip/
ground on ring
High-resistance loop
Ground on tip/
battery on ring
Ground on tip/
battery on ring
High-resistance loop
August 2005
Far end
CO
High-
loop
CO places a low resistance between tip and
ring.
Near end detects increase in loop current
and makes trunk busy to all outgoing calls.
CO applies addressing to the trunk in the
form of battery-ground or loop pulses or
DTMF tones.
Near end detects addressing, alerts terminal
A, and provides ringback tone to CO.
When terminal A goes off hook, near end
trips ringback tone and provides answer
super-vision by reversing battery and ground
on tip and ring.
If far end disconnects first, CO opens the
loop.
Near end detects drop in loop current and
reverses battery and ground on tip and ring.
If near end disconnects first, it reverses
battery and ground on tip and ring.
CO detects battery/ground reversal and
opens loop.
B
Remarks
553-AAA1138