Nortel Circuit Card Installation Manual page 600

Page 600 of 906
Figure 135
Two-way, loop OAID, TIE trunk call connection sequence – incoming call from far-end PBX
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
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
PBX
High-
loop
Far end PBX seizes trunk by placing a low
resistance between tip and ring.
Near end detects increase in loop current
and makes trunk busy to all outgoing calls.
Far end sends battery-ground or loop
pulses, or DTMF tones.
Near end detects addressing and alerts
terminal A.
Terminal A goes off hook. If answer
supervision is required by far end, reverse
battery and ground are applied to tip and ring.
Far end monitors loop current during 2-way
voice connection.
If far end disconnects first, it opens the loop.
Near end detects drop in loop current and
restores normal battery and ground.
If near end disconnects first, it reverses
battery and ground on tip and ring.
Far end detects battery/ground reversal and
opens loop.
B
Remarks
553-AAA1146