Nortel Circuit Card Installation Manual page 583

Figure 122
Ground start call connection sequence – outgoing call to CO/FX/WATS
A
Near end
System
State
Idle
Trunk seizure
Dial tone from CO
B rings
2-way voice
connection
B goes on hook
Idle
A goes on hook
Idle
Signal/direction
Tip open/
High-
resistance
loop
Ground on ring
Ground on tip/
battery on ring,
Low-resistance loop
Address signaling
Ringback
Tip open/
battery on ring
High-resistance loop
High-resistance loop
Tip open/
battery on ring
NT8D14 Universal Trunk card
Far end
CO
battery
on ring
Terminal A dials trunk access code. CE sends a
message via the data output bus to ground the ring.
dial tone
When the CO recognizes seizure, it grounds the tip
and supplies dial tone.
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.
Digits are outpulsed in the form of a series of loop
pulses or DTMF tones.
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.
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.
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.
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.
Circuit Card
Page 583 of 906
B
Remarks
Description and Installation
553-AAA1136