Nortel Networks Circuit Card - Manual (Page 586)

Page 586 of 906 NT8D14 Universal Trunk card
553-3001-211 Standard 3.00 August 2005
Figure 124
DID trunk, loop DR call connection sequence – incoming call from CO
A
State
Idle
Idle
Trunk seizure
Outpulsing
A rings
B goes on hook
Idle
A goes on hook
Remarks Signal/direction
Near end
System
B Far end
CO
High-
resistance
loop
Address signaling
High-resistance loop
High-resistance loop
Ground
on tip/
battery
on ring
Ground on tip/
battery on ring
Ground on tip/
battery on ring
Low-resistance 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.
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.
2-way voice
connection
Battery on tip/
ground on ring
Ringback
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 near end disconnects first, it reverses
battery and ground on tip and ring.
CO detects battery/ground reversal and
opens loop.
553-AAA1138