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NT8D14 Universal Trunk card Page 571 of 894
Circuit Card Description and Installation
Figure 119
Ground start call connection sequence – outgoing call to CO/FX/WATS
A
State
Idle
Idle
B rings
Trunk seizure
Dial tone from CO
B goes on hook
Idle
A goes on hook
RemarksSignal/direction
Near end
System
B
Far end
CO
Tip open/
battery
on ring
Tip open/
battery on ring
Ringback
Tip open/
battery on ring
High-
resistance
loop
Ground on ring
When the CO recognizes seizure, it grounds the tip
and supplies dial tone.
When terminal B answers, ringing is tripped and CO
cuts terminal B through to trunk. Some COs may
reverse battery and ground on tip and ring when
terminal B answers or for toll denial.
Upon receipt of the first pulse/tone, the CO removes
dial tone. When outpulsing is complete, terminal B is
rung (if idle) and the proper audible indication is
returned to local end.
If far end disconnects first, CO removes ground from
tip. If battery and ground were reversed when call
was established, battery is removed from tip and
restored to ring.
Near end detects drop in loop current and opens loop.
Digits are outpulsed in the form of a series of loop
pulses or DTMF tones.
2-way voice
connection
Ground on tip/
battery on ring,
dial tone
Low-resistance loop
High-resistance loop
High-resistance loop
Address signaling
Detection of the ground on tip is signaled to the CE
via the data input bus. The CE then sends a signal via
the data output bus to place a low-resistance loop
across the tip and ring and remove ground from ring.
Terminal A dials trunk access code. CE sends a
message via the data output bus to ground the ring.
If near end disconnects first, it opens the loop.
CO detects drop in loop current and removes ground
from tip. If battery and ground were reversed when
call was established, battery is removed from tip and
restored to ring.
553-AAA1136