Chapter 1. System Overview and Modes of Operation
34
T1 Interface Units
Coastcom offers five interfaces to the T1 transmission lines for various types of applications.
There are three versions of the Dual Channel Service Unit (CSU) Interface (with integral CSU
functionality), and two versions of the Dual Digital Service Cross-Connect DSX-1 Interface (with
no CSU functionality).
Dual CSU Interface
The Dual CSU interface offers dual DS1 interfaces for D/I Mux III. The Dual CSU
interface provides either a Channel Service Unit (CSU) interface or a DSX-1 interface
between the T1 line and the equipment. A Dual CSU interface provides test, network, and
loop/bypass functions for both the T1-1 and T1-2 directions.
The Dual CSU interface is available in three models:
• Dual CSU interface (T1/DSX-1) (P/N 30318-101) with a CSU interface on T1-1 and a
DSX-1 interface on T1-2
• Dual CSU interface (DSX-1/DSX-1) (P/N 30318-102) with two DSX-1 interfaces
• Dual CSU interface (T1/T1) (P/N 30318-103) with two CSU interfaces
Dual CSU interfaces have a front panel power-on LED as well as access and monitor
jacks for line and equipment testing. The bantam jacks provide access for monitoring the
transmit and receive T1 lines. Access jacks allow for breaking and testing the signal.
Monitor jacks do not interrupt the signal. Dual CSU interfaces include line build-out
options at 0, -7.5, and -15 dB.
Note: The monitor jacks do not directly monitor the T1 lines. The T1 signal first passes
through a lightning protector and a repeater chip. If true T1 measurements are
required, use either a DB-15, or RJ-48, connector not already used for that circuit,
located on the back of the shelf. See Figures 3-12 & 3-13 page 3-20 for pinout
information.
Should any common equipment fail, Dual CSU Interfaces enter the bypass mode and the
shelf is looped on itself as a self-check.
In channel bank mode, the shelf outputs an Alarm Indication Signal (AIS) to the network.
If power fails in drop-and-insert mode, the T1 signal bypasses the shelf using the
equalization and repeater networks as long as -48 V DC is still applied to the shelf, or is
available from the internal AC power supply.
Dual DSX-1 Interfaces
The Dual DSX-1 Interfaces provide three main functions:
• Line equalization (optional)
• Equipment and monitor jacks for testing (optional)
• Shelf bypass contacts
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