Ringing Process; Ringing Synchronization Task; Ringing Generator Output Zero-Crossing Detection; Ringing Schedule Task - Nortel DMS-100 Series General Description Manual

3-22 Ringing in Series II peripherals

Ringing process

The LCM/RLCM ringing process performs the following tasks:
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Ringing synchronization task

The ringing synchronization task performs the following functions:
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Ringing generator output zero-crossing detection

In order to minimize unwanted voltage and current transients when ringing
relays are operated, the synchronization task operates the relays only when the
ringing generator output crosses its DC offset voltage. The zero-crossing
detection task alerts the ringing synchronization task that a zero crossing of the
ringing generator output is upcoming shortly before the actual zero crossing
occurs. If the ringing synchronization task must operate or release a ringing
relay, it does so at that time.

Ringing schedule task

The ringing schedule task performs the following functions:
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Accepting/rejecting ringing and ANI/coin requests
Upon receiving a ringing or ANI/coin request from the DMS-100 CC, the
ringing schedule task verifies that the request is directed to a valid line. If the
line is valid, the ringing schedule task queues the request for processing, then
instructs the line supervision processes to monitor the line and report when the
line is answered.
Processing ringing and ANI/coin cancel messages
Upon receiving a ringing cancel request from the DMS-100 CC, the ringing
schedule task sends a message to the ringing synchronization task instructing
it to release the ringing relay for the line.
297-1001-131 Standard 06.01 October 2000
ringing synchronization
ringing generator output zero-crossing detection
ringing scheduling
waits for messages from the ringing schedule task to operate or release
ringing relays
informs the ringing schedule tasks of upcoming subcycle transitions
measures the time between subcycle transitions
verifies that the ringing generator is not overloaded
accepts or rejects ringing and ANI/coin requests from the DMS-100 CC
processes ringing and ANI/coin cancel messages from the DMS-100 CC
processes the ringing and ANI/coin request messages.