PairGain HiGain-ETSI RS UTU 712, Руководство пользователя

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Functional Description 700-712-100-01, Revision 01
18 May 10, 1999 UTU-712 and ETU-762 List 1
Table 10 summarizes the equivalent loopbacks for two different activation methods:
•
LTU and NTU LOC and REM buttons
•
Console screen Test menus (see “Testing” on page 57 for loopback operation from the Test menus).
BER T
ESTING
The HDSL units provide a mechanism for validating circuit integrity utilizing a pseudorandom bit sequence
(PRBS) generator and BER meter internal to the LTU unit. This diagnostic test disrupts the normal flow of
payload traffic, and requires the presence of a Network NTU-I/F loopback or an external physical loopback at the
NTU interface connector. The test is run at the selected HDSL Payload Rate (see
Table 15 on page 35 ). BER
results are accumulated continuously and updated on the console screen at intervals of approximately 16 seconds.
The PRBS data pattern is always generated at the LTU toward the HDSL channel, and the BER is always
measured at the LTU based on data received from the HDSL channel. The test may be initiated and stopped from
the Test menu at either the LTU or NTU console screen.
Table 10. Loopback Equivalents
Front Panel Console Screen Test Menu Data Port Control Signals
Loopback mode Loopback Position LTU Nx64k port NTU Nx64k port
LTU LOC button NETWORK
(a)
LTU-HDSL LL
LTU REM button NETWORK NTU-I/F RL
NETWORK LTU-I/F
NTU LOC button CUSTOMER
(b)
NTU-HDSL LL
NTU REM button CUSTOMER LTU-I/F RL
CUSTOMER NTU-I/F
(a) Activated from console screen Test menu at LTU.
(b) Activated from console screen Test menu at NTU.
The BER test must be stopped before leaving the test menu in order to restore
normal payload transmission. Escaping while the BER test is in progress causes
the following message to display:
“
BER Test in Progress. Must STOP
before leaving screen
.”