APPENDIX F
Common Module
A generic term for any module that, when removed, will cause a major alarm.
This includes all modules housed in the main shelf plus the Expansion Modules
located on each Expansion Shelf.
Communications Bus
See MP bus.
Control Data
Data characters that are sent serially along with data. These characters cause
functions such as framing, addressing, synchronization, and error checking to
be performed. Control data are also used to indicate handshaking protocol.
DACS Network
DACS (Digital Access Cross-connect System) is a byte oriented (DS0) digital T1
network service.
Dial Backup
A feature that provides a direct node to controller link if normal supervisory
communication between the node and controller is disrupted. Dial Backup estab-
lishes the link using the Internal GDC 212A modem on the Redundancy Control
Module or the use of an external modem.
Diversity
The term for two aggregate trunk lines between the same nodes if one trunk is op-
erational and the other is in stand-by in case the first goes down. Both lines are
monitored for serviceability by firmware on the Aggregate Control Module.
Switching of the line is controlled independently at both ends by the Aggregate
Control module.
DS0 (Digital Signal
Level 0)
A single 64 kHz channel. The data stream is divided into 8-bit bytes. DS0 is a
byte-oriented environment. An example of DS0 is the DACS network.
DS1 (Digital Signal
Level 1)
A combination of 24 DS0 channels and 8000 framing bits into a 1.544 Mbps data
stream.
DSX-1 Interface
Converts a formatted data signal into the proper signal levels for the digital T1
network. Also called a cross-connect.
ESF- ESF (Extended
Superframe)
A modified D4 framing format. The basic D4 framing structure contains 1 frame
bit followed by 24 eight-bit time slots or a 193 bit frame. An ESF contains (24) 193
bit frames. ESF allows a greater amount of access to digital network services.
Expansion Shelf
Shelf that holds up to 16 Channel Modules and 2 Expansion Modules (one pri-
mary, one redundant). Since one Channel Interface Module can interface up to 64
channels, at maximum a Channel Interface Module is connected to 4 Expansion
Shelves.
Fast Bus
Also known as the 16.896 MHz, "Common equipment" Bus, it carries controls and
data between the Channel Interface and the Aggregate Control Modules in the
node. One bit of data is conveyed by every clock bit on this bus. Physically, it
spans across the Main Harness Card.
Hertz (Hz)
bits per second transmitted or received.
Intelligent Automatic
Rerouting
A system that automatically determines proper routing of circuits around any
failed node or facility.
ISDN
Integrated Services Digital Network
Main Harness Card or
Main Harness Back-
plane
This assembly is covered by the back panel of the Main Shelf. It is covered by the
external connectors used by all the modules in the Main Shelf. Three buses on the
Main Harness Card enable the modules to communicate with each other. These
three buses are the Fast Bus, the MP Bus (or Communication Bus), and the Clock
Bus.
Module
An assembly which has definable performance characteristics so that it can be
tested, removed, and replaced as a unit. A module can have other cards called
"piggybacks" plugged into it.
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