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64291043SAALL-5E
Section 64291043SAALL-5, Issue 5
CSU Latching Loopback
Some test systems embed All-1s Repeater Release
Codes within the CSU Latching Loopback command
to bypass loop repeaters and directly access the DSU/
CSU. If a latching loopback at the Total Reach
DDS-R is desired, see subsection
Network Interface
Equipment Latching Loopback
on this page
.
See Table
4 for latching loopback sequences.
For test systems or test sets that do not support
automatic release of CSU latching loopback from the
repeaters or network interface devices, use the
following procedures.
Initiating CSU Latching Loopback to Loop
DDS-R (SW1-1 LBK enabled)
•
From a test system or set, send a CSU latching
loopback sequence. This instructs the TROCU
DP to notify the Total Reach DDS-R of a CSU
loopback request.
•
Send a selected test pattern and test for error-free
operation.
•
Upon completion of this test, advance to
subsection
Terminating CSU Latching Loopback
to Total Reach
DDS-R or DSU/CSU
for latching
loopback termination.
Initiating CSU Latching Loopback to Loop a
DSU/CSU (SW1-1 LBK enabled)
•
From a test system or set, send a CSU latching
loopback sequence. This instructs the TROCU
DP to notify the Total Reach DDS-R of a CSU
loopback request.
•
To release the Total Reach DDS-R from latching
loopback and reverse sealing current to the DSU/
CSU, send the non-latching CSU loopback code
alternating with an All-1s data pattern for
approximately 2 seconds. The DSU/CSU should
loop when reversed sealing current is detected.
•
Send a selected test pattern and test for error-free
operation.
•
Upon completion of this test, advance to
subsection
Terminating CSU Latching Loopback
to Total Reach
DDS-R or DSU/CSU
for latching
loopback termination.
Terminating CSU Latching Loopback to Total
Reach DDS-R or DSU/CSU
• From a test system or set, send a CSU Latching
Loopback Disable command (35 TIP bytes).
Network Interface Equipment Latching
Loopback
The NIE latching loopback method can be used to loop
the Total Reach DDS-R at all rates. This loopback test
may require programming of the loopback select code
or the complete sequence into the test system.
5. DEPLOYMENT GUIDELINES
The TROCU DP and Total Reach DDS-R use
technology intended to eliminate the need for repeaters
and concerns over impairments caused by typical noise
and bridged tap. Listed below are the loop design
guidelines for Total Reach DDS (see
Table 6
and
Table 7
for more information):
• All loops must be nonloaded.
• Actual Measured Loss (AML) should not exceed
50 dB at 13.3 kHz (135
Ω
termination), the
Nyquist frequency of Total Reach DDS.
NOTE
The 50 dB AML limit includes 6 dB of signal
margin to account for potential near-end cross
talk (NEXT) from other digital services that may
be provisioned in the same binder group.
• Loop length should not exceed 50 kft.
• Bridged tap length should not exceed 12 kft.
• Background noise level should not exceed
34 dBrn.
• Impulse noise level should not exceed
-40 dBm, (+50 dBrn).
NOTE
Measure noise with 50 kbit weighting
characteristic approximating a filter with a
passband of 40 Hz to 30 kHz. Background noise
level or impulse noise level is referenced from
56/64 kbps data rate in TR62310.
6. MAINTENANCE
The Total Reach DDS-R Standalone does not require
routine maintenance for normal operation.
