Specifications

Ringing in Series II peripherals 3-23

DMS-100 Ringing System

Upon receiving a ANI/coin cancel message, the ringing schedule task sends a

message to the ringing synchronization task instructing it to release the

ANI/coin voltage relay from the line.

Ringing and ANI/coin messaging

Ringing and ANI/coin requests that are queued by the ringing schedule task

are processed by a ringing state machine or ANI/coin state machine that is

driven by the ringing schedule task. The ringing schedule task drives the

ringing and ANI/coin state machines through state transitions (changes in

ringing signal or ANI/coin voltage applications). State machine transitions are

caused by one of four events.

• The ringing schedule task receives a time-out message: A timer set by a

previous state machine on a speciﬁc line timed out, and a time-out message

was sent to the ringing schedule task. In response, the ringing schedule task

activates the ringing or ANI/coin state machine speciﬁed in the time-out

message.

• The ringing schedule task receives a message from another task: A

message indicating that an event has occurred was received from a state

machine or another task. The ringing schedule task then activates the

ringing or ANI/coin state machine speciﬁed in the message.

• The ringing schedule task received a time-out message indicating a slot

transition: The ringing schedule task then performs the following tasks:

— determines the length of the next time slot from a table of time slot

lengths stored in memory, which is indexed by slot numbers

— sets a timer to the length of the next time slot as found in the timeslot

table

— invokes the ANI/coin state machine for any ANI/coin processes

required for this time slot

— checks the ringing service queue for any transition requests for this

time slot and invokes the ringing state machine for any lines requiring

ringing state transitions

— invokes the ANI/coin state machine for the ANI/coin function if an

ANI/coin function is required for this time slot

If no ANI/coin function is required for this time slot, the ringing

schedule task attempts to service the next ANI/coin request in the

queue. The ringing schedule task checks to see if the ringing bus in the

Line Drawer requiring the ANI/coin function is idle for the next slot (or

the next two slots if it is 4-party ANI/coin function). If the ringing bus

is idle, the ringing schedule task services the request.

• The ringing schedule task received a subcycle transition message from the

ringing synchronization task: The value of the time slot number is updated