Nortel DMS-100 Series Maintenance Manual page 42

1-26 Maintenance overview
The SMS call processing and call control features monitor and control these
activities through signals and messages sent to the RCS. The DDL link and
A- and B-signaling bits compose these messages.
Call processing software modules
The following list includes SMS software modules that initiate call control
operations for line circuits, subscriber loops, and telephone sets:
The relationship of these modules appear in the following diagram. A
description of each module appears after the diagram.
297-8231-550 Standard 09.01 August 1998
send dial tone to an off-hook subscriber that originated a call
scan for and collecting digits
ring a subscriber line
send audible ringback tone to a calling subscriber
trip ringing on a called subscriber when that subscriber goes off-hook
disconnect the call-holding bridge on telephone keysets.
terminal processing task (TPT)
derived data link (DDL) facility
the A/B-bit facility
the UP ringing task
the SMS maintenance