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TDM-BUS (TDM Bus)
Issue 1 June 2005 2237
TDM-BUS (TDM Bus)
S8700 | 8710 / S8500
Description
Each port network has a pair of TDM buses, designated TDM bus A and TDM bus B, each with
256 time slots. This division allows for duplication of control channels and dedicated tone time
slots. The first five time slots on each bus are reserved for the control channel, which is active
on only one bus at a time in each port network. The next 17 time slots are reserved for system
tones such as dial tone, busy tone and so on. As with the control channel, these time slots are
active on only one bus, A or B, at a time. The rest of the time slots on each bus are for general
system use such as carrying call-associated voice data. The 17 dedicated tone time slots that
are inactive can also be used for call processing when every other available time slot is in use.
When the system initializes, the control channel is on TDM bus A and the dedicated tones on
TDM bus B in each port network. If a failure occurs on one of the two buses, the system will
switch any control, tone and traffic channels to the other bus. Service will still be provided,
though at a reduced capacity.
The set tdm PC command has the effect of putting both the control channel and tone time
slots on a specified bus, A or B. P specifies the port network’s number, and C specifies the TDM
bus, A or B. Throughout this discussion, PC refers to a specific TDM bus. References to port
circuit packs include every circuit pack that terminates on the TDM bus, including the Expansion
Interface TN570, and the following service circuit port boards: Call Classifier (TN744),
Integrated Announcement (TN750), Maintenance/Test (TN771), Speech Synthesizer (TN725B),
Tone Detector (TN748 or TN420). Other terms used are:
● Control Channel Bus: the TDM bus carrying the active control channel
● Non-Control Channel Bus: the TDM bus with the inactive control channel
● Tone Bus: the TDM bus carrying the active tone time slots
● Non-Tone Bus: the TDM bus with the inactive tone time slots
MO Name Alarm Level Initial Command to Run
1
1. P is the port network number. Use list cabinet to find the port network(s)
contained in a cabinet.
Full Name of MO
TDM-BUS MAJ test tdm P TDM bus
TDM-BUS MIN test tdm P TDM bus
TDM-BUS WRN test tdm P TDM bus