Zte ZXDSL 9210 (V3.1), Техническое руководство

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to even channels of subscriber lines are converged; all test and protective buses are
converged to the LTC, which implements protective switchover and tests.
The operating principles of the VTIEF are illustrated in Fig. 4.2-5.
Over-current and
over-voltage
protection
components
PSTN
VTIEF
Subscriber
line
2 pairs of test
buses
2 pairs of
protection buses
Splitter
Relay
Relay
VSET board
Fig. 4.2-5 Operating Principles of VSET
4.2.5 PSUN/PSUT
4.2.5.1 Functions of ADSL Splitter Board
The ADSL splitter board is used to detach voice signals from ADSL signals, to avoid
the impacts such as telephone hook-on/hook-off and interferences on the performance
and reliability of the ADSL line. If the line test protection is implemented in the system,
the splitter board provides not only signal separation function, but a group of handover
to protective buses used to provide M+1 protection. Besides, it provides a test bus to
test external lines. In this case, the splitter board used is PSUT.
4.2.5.2 Operating Principles of ADSL Splitter Board
The PSUN board is actually a low-pass filter group. Signals on a subscriber line
(mixture of digitals and voice) will pass through the over-current and over-voltage
protection devices. Then low-pass filtration will be performed via a 2-level transformer
and other peripheral auxiliary devices, where high-frequency and interfering signals are
eliminated. Data signals and voice signals on the subscriber line are split, and
low-frequency voice signals filtered will then be sent to a PSTN switch to be
transferred.