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Page 576 of 894 NT8D14 Universal Trunk card
553-3001-211 Standard 2.00 September 2004
Figure 123
Two-way, loop DR, TIE trunk call connection sequence – incoming call from far-end PBX
A
State
Idle
Idle
Trunk seizure
Outpulsing
A rings
B goes on hook
Idle
A goes on hook
RemarksSignal/direction
Near end
System
B
Far end
System
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
Far end places a low resistance between tip and ring.
Near end detects increase in loop current and makes
trunk busy to all outgoing calls.
Far end applies addressing to the trunk in the form of
battery-ground or loop pulsing, or DTMF tones.
Near end detects addressing, alerts terminal A, and
provides ringback tone to far end.
When terminal A goes off hook, near end trips ringback
tone and provides answer supervision, if required by far
end, by reversing battery and ground on tip and ring.
If far end disconnects first, it momentarily opens the loop
and then restores normal battery and ground if no near-
end answer supervision was provided when call was
establish-ed. Otherwise, it waits for the near end to
restore normal battery and ground.
Near end detects drop in loop current and restores normal
battery and ground if answer supervision was provided.
Otherwise, terminal A simply hangs up.
If answer supervision was provided, far end restores
normal battery and ground when it detects
battery/ground reversal from near end.
2-way voice
connection
Battery on tip/
ground on ring
Ringback
If near end disconnects first, normal battery is restored if
answer supervision was provided to establish call.
Otherwise, terminal A simply hangs up.
If far end detects battery/ground reversal, it
momentarily opens loop and then restores normal
battery. But, if no answer supervision was provided by
the near end when the call was established, it cannot
supply a battery reversal to signal call termination; the
person at terminal B must recognize end of call and
hang up, which will then cause the far end to restore
normal battery.
553-AAA1140