Verilink AS2000: The Basics (880-502981-001) Product Manual - Manual (Page 21)

System Information
Verilink Access System 2000: The Basics 2-5
longest uptime becomes the new node master. In a node containing
a single shelf, an NCM module is usually both the node and shelf
master.
The shelf and node ACP masters can be determined by the status of
the LEDs. See the section
“Front Panel LED Indicators“ in Chapter 4
for more information.
Types of Modules
Application modules contain the hardware and firmware to
construct different service roles. There are three functions the
AS2000 system application modules can perform. Channel Service
Units (CSUs), Data Service Units (DSUs) and Node Controller Units
(NCM, NCC, etc.). An application module’s port configuration is
determined by selecting the appropriate Connector Interface
Module (CIM). The configuration data is stored within each
module, and can be retrieved or edited.
Channel Service
Unit Modules (CSU)
The CSU terminates network services at the customer premises,
and connects a Wide Area Network (WAN) to application equipment.
Each CSU can be configured for a desired mode of operation. The
CSU can connect directly to DS1 or CEPT-1 equipment, to one or
more DSUs (if MUX mode is available), or both.
CSU Operating Modes
CSUs can operate in one or two of three possible modes: CSU mode,
multiplexer mode (MUX), and drop-and-insert mode (D&I). All CSUs
interface to the Network Service Provider (NSP) ports. The
configuration on the Equipment side of the CSU in each mode is
described in
Table 2-1 . Figure 2-4 provides a graphic view of the
three CSU modes.