Nortel Circuit Card Installation Manual page 602

Page 602 of 906
Figure 137
Two-way, loop OAID, TIE trunk call connection sequence – outgoing call to far-end PBX
A
Near end
System
State
Idle
Trunk seizure
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
Battery on tip/
ground on ring
Low-resistance loop
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
Terminal A goes off hook and dials access
code. Near end reverses battery and ground
on tip and ring, alerting far end.
Far end detects battery/ground reversal and
answers call by placing a low resistance
between tip and ring.
Near 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
reverses battery and ground on tip and ring.
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-AAA1148