Filter
Top Products
Testing
5-2
7510-A2-GB20-10
November 1997
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 Notes
Bilateral Loopback H User
H Remote unit sending
V.54 sequence
When enabled, running a DSU loopback
also automatically starts a local
loopback. Refer to Table A-3, Data Port
Options, to enable.
CSU Loopback H User (Network tests)
H DDS Network, by
loop current reversal
When initiated by the network, CSU
Loopback cannot be disabled by the
user.
DSU Loopback
(Digital)
H User Refer to Table A-3, Data Port Options.
Local Loopback H User
H DTE via CT141
Control via CT141 can be disabled.
Refer to Table A-3, Data Port Options.
Network-initiated
56 kbps DSU
Loopback (Non-
latching loopback)
H DDS Network Cannot be disabled by user.
Network-initiated
64 kbps CC DSU
Loopback
(Latching loopback)
H DDS Network Includes optional data scrambling and
uses 25-second timer to detect the
network sequence. Can be disabled by
user.
Remote Digital
Loopback
H Remote unit sending
V.54 sequence
Same as a DSU Loopback but initiated
by a remote unit via V.54 sequence.
Can be disabled locally. Refer to
Table A-2, Network Interface Options.
V.54 Sequences to
remote unit
H User
H DTE via CT140
Control via CT140 can be disabled.
Refer to Table A-3, Data Port Options.