ADTRAN SHDSL NxNTU specifications Loopback Overview, VT100 Test Screens

Loopbacks may be initiated via the VT100 test screens, front panel pushbuttons, Nx64K port control leads, or by receiving V.54 or PN127 in-band looping signals. Not all loopback types are available for all

ports and port services by all initiating sources. See Table 9 for an overview. A key to the symbols displayed in Table 9 is available below the Table.

Table 9. Loopback Overview

	Ports
	Customer, away		Network, toward SHDSL		Services
Initiating Source	from SHDSL Port (left)		Port (right)
	Nx64k Port	G.703 Port		SHDSL Port	G.704 Service	Nx64k Service
		VT100 Test Screens
VT100 Loopback On
(Initiates one of five
loopback types,
regardless of the	AIS	AIS		AIS	AIS	(Same as
associated Loopback
Type Option setting.)*						Nx64k Port)

AIS

AIS

AIS

AIS

VT100 Loopback Off

LL Button On										Single
(Initiates a Local										service
Customer Loopback per										only	(Same as
the selected port Loopback
Type Option setting)	AIS			AIS		AIS			AIS		Nx64k Port)
LL Button Off
RL Button On		Sends					Sends			Single
(Initiates a Remote										service
							EOC
Network Loopback per		In-Band		N/A						only
							Request				(Same as
the remote unit’s selected		Patterns
							Message
port Loopback Type	AIS								AIS		Nx64k Port)
						AIS
Option setting)*
RL Button Off		Sends					Sends			Sends
		In-Band					EOC			In-Band
		Patterns					Request			Patterns
							Message
			Nx64k Port Control Leads
C141 LL On			N/A		N/A			N/A
(Initiates a Local
Customer Loopback											(Same as
per the Nx64k port
Loopback Type Option	AIS										Nx64k Port)
setting)
C141 LL Off			N/A		N/A			N/A
C140 RL On		Sends	N/A		N/A			N/A
(Initiates a Remote
Network Loopback		In-Band									(Same as
per the remote unit		Patterns
Nx64k port Loopback	AIS										Nx64k Port)
Type Option setting)*
C140 RL Off			N/A		N/A			N/A

In-band Looping Protocol Reception

Receive In-band Preparatory Signal

(Applies the loopback after detection of in-band V.54 or PN127 remote looping pattern per the associated service Loopback Type Option setting)

Receive In-band Termination Signal

(Terminates loopback after detection of in-band V.54 or PN127 remote looping pattern)

(Same as Nx64k Service)

N/A

N/A

N/A

AIS AIS

N/A

Key:

Dual Loop Transparent Loop AIS Nontransparent Loop No Loop

*The reception of in-band loopback patterns and EOC loopback request messages may be ignored or blocked on certain SHDSL LTUs installed in Total Access 3000 Systems

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