39
40
To perform an RDL test, follow these steps:
1. Activate RDL. This may be done in two ways:
a.
Enter Remote Loop from the System
Diagnostics/Statistics menu and toggle the [Spacebar]
until “RL” appears next to the
Remote Loop option.;
b.
Activate the “RL” signal on the DTE. If you are not sure
which lead is the “RL” signal, please refer to Appendix D.
2. Perform a bit error rate (BER) test using the internal V.52 gen-
erator (as described in Section 5.3), or using a separate BER
Tester. If the BER test indicates a fault, and the Local Line
Loopback test was successful for both Model 2710As, you
may have a problem with the twisted pair line connection.
5.2.3 Central Office Loops
The Model 2710A also responds to central office initiated loop com-
mands. When in D4 framing mode, the Model 2710A will implement
the “loop up” command when it recognizes the pattern “10000” in the
data stream for a minimum of 5 seconds. The “loop down” command is
implemented by the pattern “100” in the data stream for a minimum of
5 seconds.
When operating in ESF framing mode, loopback commands are
issued via the Facility Data Link (FDL). The line loop message will
cause a loop back before data enters the framer portion of the CSU.
The payload loop message will cause the Model 2710A to loop data
after the framer portion of the CSU.
The Model 2710A will respond to Universal Loopback De-activate
to clear all central office loops.
5.3 BIT ERROR RATE (V.52) DIAGNOSTICS
The Model 2710A offers three V.52 Bit Error Rate (BER) test pat-
terns. These test patterns may be invoked along with the LAL and
RDL tests to evaluate the unit(s) and the communication links.
When a 511, 2047, or QRSS test is invoked, the Model 2710A
generates a pseudo-random bit pattern of 511 bits, 2047 bits or 2
20
bits,
respectively, using a mathematical polynomial. The receiving Model
2710A then decodes the received bits using the same polynomial. If
the received bits match the agreed upon pseudo-random pattern, then
the Model 2710A(s) and the communication link(s) are functioning
properly.
511
Initiates a built-in 511 bit pseudo-random pattern
generator and detector.
2047
Initiates a built-in 2047 bit pseudo-random pattern
generator and detector.
QRSS
Initiates a built-in 2
20
bit pseudo-random pattern gen-
erator and detector.
To perform a V.52 test, follow these steps:
1.
Activate the local loopback or remote loopback diagnostic.
2. Activate the test pattern. This may be done in one of two
ways:
a. Enter Selected Pattern from the System
Diagnostics/Statistics menu and toggle the [Spacebar]
until the desired test pattern appears.
b. Enter Test Pattern and toggle the [Spacebar] to send
the selected pattern.
c. One of two result codes will appear to the right of the
Test Pattern listing:
OK Indicates that the received test pattern is error-free.
BE Indicates that there are errors in the test pattern (to
deliberately insert errors in the pattern, toggle
Error Insertion to ON).
b
b
c
d
c
e
