Nortel DMS-100 Series General Description Manual page 93

Figure 3-8 LCM ringing sequence diagram
D D M M S S - - 1 1 0 0 0 0 C C C C
Sends ringing request
1
message indicating line
to be rung
D D M M S S - - 1 1 0 0 0 0 C C C C
Ringing schedule task verifies request is directed to
2
valid line and channel is associated with line
Ringing schedule task sends request accepted
3
message (if required by DMS-100 CC)
Ringing schedule task copies ringing request
4
message into call data block associated with call
Ringing schedule task instructs supervisory tasks to
5
scan terminating line for answer
Timer notifies ringing schedule task of upcoming
6
time slot transition
Ringing schedule task determines length of next
7
time slot and starts timer for this length
Ringing schedule task examines ringing request
8
queue, determines which ringing requests require
state transition in next time slot, and initiates ringing
state machine for those requests
Ringing schedule task operates and releases ringing
9
relay on terminating line card through ringing
synchronization task
Ringing schedule task continues driving ringing
10
state machine
When called party answers, supervisory task notifies
11
ringing schedule task that called party has gone
off-hook
Ringing schedule task removes ringing request for
12
called party from ringing request queue
If line is ringing when off-hook is detected, ringing
13
schedule task instructs ringing synchronization task
to release ringing relay on line card of called party
14
LCM sends answer message to DMS-100 CC
15
Call enters talking state
Ringing in Series II peripherals 3-25
L L C C M M
DMS-100 Ringing System