xDSL:  General Configuration
      (Appendix B Chart Description)

     The Chart illustrates xDSL, a telecommunications
service transmission technology.  With xDSL technology, two
xDSL modems are attached to each telephone loop:  one at the
subscriber's premises, and one at the telephone company's
central office.  The use of xDSL modems allows transmission
of data over the copper loop at vastly higher speeds than those
used for voice telephony or analog data transmission.  A
subscriber, using xDSL technology, can potentially make
ordinary voice calls over the public switched network at the
same time as he or she is using the same line for high-speed
data transmission.

     In circumstances in which the xDSL-equipped line
carries separate POTS ("plain old telephone service") and data
channels, the carrier must separate those two streams when
they reach the telephone company's central office.  This is done
in a device known as a digital subscriber line access
multiplexer, or DSLAM.  The DSLAM and central office
xDSL modem send the customer's POTS traffic to the public,
circuit-switched telephone network.  The DSLAM sends the
customer's data traffic (combined with that of other xDSL
users) to a packet-switched data network.  Thus, the data
traffic, after traversing the local loop, avoids the circuit-
switched telephone network altogether.

     Once on the packet-switched network, the data traffic
is routed to the location selected by the customer, for example,
a corporate local area network or an Internet service provider. 
That location may itself be a gateway to a new packet-
switched network or set of networks, like the Internet.

        Digital Loop Carrier System
      (Appendix C Chart Description)
     The Chart illustrates the use of digital loop carrier
systems.  A traditional copper loop typically runs from the
network interface device at the customer's premises to the
LEC's central office.  Because of voice transmission quality
degradation and maintenance challenges associated with long
copper loops, along with the economic efficiencies associated
with aggregating individual loops, LECs have begun to deploy
remote concentration devices, such as digital loop carrier
(DLC) systems.  DLCs convert analog signals, from many
copper loops that terminate at a remote terminal, into digital
signals, multiplex the signals, and transport them, usually over
fiber, to the central office.