Paradyne 727 manual Testing, 1.Device Messages, Loopback Type, Initiated By

Testing

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

V.54 Sequences to remote unit

HUser

HDTE via CT140

Control via CT140 can be disabled. Refer to Data Port Options, Table A-3.

5-2 March 1997 7510-A2-GB20-00