ADTRAN AHDSL2 specifications Table A-1. In-Band Addressable Loopback Codes

	Table A-1. In-Band Addressable Loopback Codes
Function	Code	Response
1 in 31	100	Loop down everything.
1 in 61	100000	Loopback at the H2TU-R toward the network; must be armed before
		initiated.
4 in 7	1111000	Loopback data from network toward network in the H2TU-C.
6 in 7	1111110	Loopback data from customer toward customer in H2TU-C.
FF1E	1111 1111 0001	Loopback data from network toward network at H2TU-C.
	1110
3F1E	0011 1111 0001	Loopback data from customer toward customer at H2TU-C.
	1110
Arm1 (also known	11000	If the pattern is sent from the network, the units will arm and the H2TU-R
as 2-in-5 pattern)		will loop up toward the network. No AIS or errors will be sent as a result
		of this loopback. If the pattern is sent from the customer, all units will
		arm.
Arm (ESF Data	FF48	If the pattern is sent from the network, the units will arm and an H2TU-R
Link)	1111 1111 0100	network loopback will be activated. This code has no functionality when
	1000	sent from the customer.
Disarm1 (in-band)	11100	When sent from the network or customer, all units are removed from the
(also known as		armed state and loopbacks will be released. If any of the units are in
3-in-5 pattern)		loopback when the 11100 pattern is received, they will loop down. The
		LBK LEDs will turn off on all units.
Disarm1	FF24	When sent from the network or customer, all units are removed from the
(ESF Data Link)	1111 1111 0010	armed state and loopbacks will be released.
	0100
H2TU-C Network	D3D3	If the units have been armed and no units are in loopback*, the H2TU-C
Loop Up1, 2	1101 0011 1101	will loop up, 2 seconds of AIS (all ones) will be transmitted, the looped
	0011	data will be sent for 5 seconds, and then a burst of 231 logic errors will be
		injected. The burst of 231 logic errors will continue every 20 seconds as
		long as the D3D3 pattern is detected. When the pattern is removed, the
		unit will remain in loopback. If the pattern is re-instated, the injection of
		231 logic errors will continue every 20 seconds. If the pattern is sent from
		the network, the loop up and error injection will be toward the network. If
		the pattern is sent from the customer, the loopback and error injection will
		be toward the customer.
H2TU-R Address	C754	When sent from the customer, an H2TU-R network loopback is activated
20 for extended	1100 0111 0101	and a 200-bit error confirmation is sent. Two seconds of AIS (all ones)
demarc1	0100	will be sent, 5 seconds of data will pass, and then 200 bit errors will be
		injected into the DSX-1 signal. As long as the pattern continues to be sent,
		200 errors will be injected every 20 seconds. The HDSL2 office unit will
		not block transmission of far end NIU loopback from the customer premise
		(H2TU-R).

Note: All codes listed above must be sent for a minimum of 5 seconds in order for them to be detected and acted upon. * If NIU is enabled, then the H2TU-R can be in network loopback when the H2TU-C loop up codes are sent.

1The H2TU-C and H2TU-R individually detect and act upon in-band loopback control codes. Depending on which list number of

H2TU-R is used with the Litespan H2TU-C, some of these control codes may not cause action (such as loop up, error injection, etc.) at the H2TU-R.

Refer to the H2TU-R documentation for supported control codes.

2Units must be armed with 11000b or FF48h before this code will work

3In order to behave like a NIU, the H2TU-R will not loop down from the network side with 9393h.

4 This code will be detected only if the units are armed OR if any loopbacks are active.

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