Paradyne 7520 User Manual page 38

Testing
5-2
Loopbacks can be started from a variety of points in the network, as shown in
Table 5-1.
Table 5-1. Device Messages
Loopback Type Initiated By
Bilateral Loopback User
Remote unit sending
V.54 sequence
CSU Loopback User (Network tests)
DDS Network, by
loop current reversal
DSU Loopback User (Network tests)
(Digital)
DDS Network
Local Loopback User
DTE via CT141
Network-initiated DDS Network
2.4 – 56 kbps DSU
Loopback (Non-
latching loopback)
Network-initiated DDS Network
64 kbps CC DSU
Loopback
(Latching loopback)
Remote Digital Remote unit sending
V.54 sequence
Loopback
V.54 Sequences to User
remote unit
DTE via CT140
Notes
When enabled, running a DSU loopback
also automatically starts a local
loopback. Refer to Table A-3,
Options, to enable.
When initiated by the network, CSU
Loopback cannot be disabled by the
user.
When initiated by the network, DSU
Loopback cannot be disabled by the
user.
Control via CT141 can be disabled.
Refer to Table A-3,
Cannot be disabled by user.
Includes optional data scrambling and
uses 25-second timer to detect the
network sequence. Can be disabled by
user. Refer to Table A-2,
Interface
Same as a DSU Loopback but initiated
by a remote unit via V.54 sequence.
Can be disabled locally. Refer to
Table A-2,
Control via CT140 can be disabled.
Refer to Table A-3,
May 1998
Data Port
Data Port Options.
Network
Options.
Network Interface Options.
Data Port Options.
7520-A2-GB20-20