Patton electronic 2500 Series - Manual (Page 16)

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CSU Loop
The CSU Loop is activated when the central office reverses the DC
sealing current that flows between the TX pair and the RX pair. In this
case, the Model 2500 Series recognizes this and loops signals on the
RX pair back to the central office on the TX pair (see Figure 8, below).
While the CSU Loop is activated by the central office, the TM light is
illuminated.
DSU Loop
The DSU Loop is activated when the central office sends a DSU
loop signal over the twisted pair wire. The Model 2500 Series senses
this signal and loops the digital data back to the central office (see
Figure 9, below). While the DSU Loop is activated, the TM light is
illuminated.
5.4 THE V.52 BER TEST PATTERN GENERATOR
The Model 2500 Series has a built-in test pattern generator and
detector. It can be invoked at both ends of a link simultaneously (using
two operators) or it can be invoked in conjunction with the LAL or RDL
tests (using one operator). The following example requires two
operators–one to initiate and monitor the test at the local Model 2500
Series, and one at the remote Model 2500 Series. To use the V.52 BER
test by itself, both operators should simultaneously follow these steps:
(continued)
1) Locate the “511/511E” toggle switch on the front panel of the
Model 2500 Series and move it DOWN (see Note 1). This
activates the V.52 BER test mode and transmits a “511”
pseudorandom test pattern to the other unit. If any errors are
received, the receiving CSU/DSU’s red “Error” LED will blink
sporadically (see Notes 1 & 2, below).
2) If the test indicates no errors are present, move the V.52 toggle
switch UP, activating the “511/E” test (see Note 2). The 511/E test
transmits the 511 pseudorandom test pattern and injects
intentional errors about once per second. If the test is working
properly, the receiving CSU/DSU’s red “Error” LED will blink
regularly.
A successful “511/E” test will confirm that the link is in place, and
that the Model 2500 Series’ built-in “511” generator and detector
are working properly.
Note 1 : The 511 BER pattern can also be activated using the
software control port. Follow these steps: From a
terminal, first go to the Main Menu and select item 3 to
display the Software Switch Menu (Section 4.2) In the
Software Switch Menu, select item “c” to go to the Send
511 Pattern Menu (see below). To send a 511 pattern,
select item 1.
Note 2 : Control Port activation of the “511E” pattern is not
possible. The “511E” pattern may only be activated using
the front panel toggle switch.
Figure 9. DSU loop
Figure 8. CSU loop