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NT8D14 Universal Trunk card Page 581 of 894
Circuit Card Description and Installation
Figure 127
Two-way, loop DR, TIE trunk call connection sequence – outgoing call to far-end PBX
A
State
Idle
Idle
Trunk seizure
Outpulsing
B rings
A goes on hook
Idle
B goes on hook
RemarksSignal/direction
Near end
System
B
Far end
PBX
Address signaling
High-resistance loop
Ground on tip/
battery on ring
Ground on tip/
battery on ring
Ground on tip/
battery on ring
Ground on tip/
battery on ring
Ground on tip/
battery on ring
Low-resistance loop
Ground on tip/
battery on ring
When terminal A goes off hook, near end places a low
resistance between tip and ring.
Terminal A dials and battery-ground or loop pulses, or
DTMF tones, are sent to far end.
If answer supervision is provided by far end, reverse
battery and ground are applied to tip and ring when
terminal B answers.
Near end monitors loop current during 2-way voice
connection.
If near end disconnects first, it momentarily opens the loop
and then restores normal battery and ground if no far-end
answer supervision was provided when call was establish-
ed. Otherwise, it waits for the far end to restore normal
battery and ground.
Far end detects drop in loop current and restores normal
battery and ground if answer supervision was provided.
Otherwise, terminal B simply hangs up.
If answer supervision was provided, near end restores
normal battery and ground when it detects
battery/ground reversal from far end.
2-way voice
connection
Battery on tip/
ground on ring
If far end disconnects first, it restores normal battery if
answer supervision was provided to establish call.
Otherwise, terminal B simply hangs up.
If near end detects battery/ground reversal, it moment-
arily opens loop and then restores normal battery. But,
if no answer supervision was provided by the far end
when the call was established, it cannot supply a
battery reversal to signal call termination; the person at
terminal A must recognize end of call and hang up,
which will then cause the local end to restore normal
battery.
553-AAA1142