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Overview
Hardware Overview
T1 Modules. If you are leasing a T1-carrier line and the public carrier does
not provide a CSU/DSU, you will need to purchase one of the three narrow
slot T1 modules, which include a built-in CSU/DSU. (See Figure 1-8.) Select:
■ a one-port T1 module, which supports a full T1-carrier line (24 channels
or 1.544 Mbps)
■ a two-port T1 module, which provides 1.544 Mbps on each interface (3.088
Mbps total)
■ a T1 + DSX-1 module, which enables you to use some channels for data
and some channels for voice
Figure 1-8. T1 Modules
Serial Module. If you lease an E1- or T1-carrier line and the public carrier
provides an external CSU/DSU, you will need to purchase the serial module.
(See Figure 1-9.)
Figure 1-9. Serial Module
ADSL2+ Annex A or Annex B Module. The ADSL2+ modules provide
bandwidth up to 25 Mbps downstream and 1.544 Mbps upstream. Because
ADSL also supports analog voice on the local loop, existing telephone equip-
ment and fax machines can continue to carry traffic on the same line. The
ADSL2+ Annex A module supports analog voice over the Plain Old Telephone
Service (POTS). The ADSL2+ Annex B module supports ISDN voice and fax
traffic. (See Figure 1-10.)
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