Nortel Networks Circuit Card - Manual (Page 43)

Overview Page 43 of 906
Circuit Card Description and Installation
Figure 6
Call connection sequence – near-end station receiving call
553-AAA1113
High-
resistance
loop
Line card unit idle
(2-way voice
connection)
Remarks
Ground on tip/
battery on ring
Signal/direction State
System
Ground on tip/
battery on ring
High-resistance loop
Ground on tip/
battery on ring
Far-end station
on hook
Near-end station
on hook
If near-end station hangs up first, the
following occurs: Line card detects drop
in loop current. CPU removes timeslot
assignments.
If far-end station hangs up first, the
following occurs: The system detects
disconnect signaling from trunk. CPU
removes timeslot assignments. Person
at near-end station recognizes end of
call and hangs up.
No battery current drawn.
Far-end station goes off hook and
addresses (dials up) near-end station.
The system receives the incoming
call on a trunk and determines that the
call is for a specific unit terminal number
(TN) and assigns message timeslots.
The system applies 20 Hz ringing to
ring lead.
Ringing
Low-resistance loop
Near-end station
off hook
Near-end station goes off hook.
Near-end
station
The system detects increase in loop
current, trips ringing, and cuts call
through to near-end station.
Line card unit is ready for the next call.
High-
resistance
loop
Line card unit is ready for the next call.
High-
resistance
loop
Line card unit idle
Line card unit idle
High-resistance loop
Far-end
station
through
PSTN
Alert