Figure 4. Hdsl2 Loopbacks - ADTRAN T200 H2TU-R Installation And Maintenance Manual

NOTE
For the MON jacks, the Tx and Rx indications
relate to the direction of the signal to/from the
CPE, respectively.
H2TU-R Network Loopbacks
The H2TU-R responds to multiple loopback activation
processes. The loopback position is a logic loopback
located within the H2TU-R internal HDSL2
transceiver. See Figure 4.
First, manual loopback activation may be
accomplished using the control port of the H2TU-R.
H2TU-C Network-Side Loopback
DSX-1
H2TU-C
H2TU-R Network-Side Loopback and/or
H2TU-R NIU Loopback
DSX-1
H2TU-C
H2TU-R Customer-Side Loopback
X
AIS
H2TU-C
H2T2-C Customer-Side Loopback
X
AIS
H2TU-C
H2TU-R Bilateral Loopback
DSX-1
H2TU-C
X = Signal Inactive
D = Data Sent

Figure 4. HDSL2 Loopbacks

61222026L7-5B
AIS
LOCAL
DS1
LOOP
X
H2TU-R
AIS
LOCAL
DS1
LOOP
X
H2TU-R
LOCAL
DS1
LOOP
H2TU-R
LOCAL
DS1
LOOP
H2TU-R
LOCAL
DS1
LOOP
H2TU-R
Section 61222026L7-5, Issue 2
Second, the H2TU-R will respond to the industry
defacto HDSL loopback codes as designated in the
ANSI document T1E1.4/92. A synopsis of the
method described by ANSI is presented in
Appendix A.
Third, the H2TU-R responds to T1 Network Interface
Unit (NIU) loopback codes as described in Bellcore
TR-TSY-000312. The NIU loopback codes are as
follows:
In-Band Codes
Loop up ....... 11000
Loop down .. 11100
ESF Codes
Loop up ....... 1111 1111 0100 1000
Loop down .. 1111 1111 0010 0100
Receiving the in-band codes for more than five
seconds or the ESF codes four consecutive times will
cause the appropriate loopback action. The ESF codes
must be transmitted in the Facility Data Link (FDL).
NOTE
The NIU loopback option must be enabled
before the H2TU-R can respond to the NIU
loopback.
The H2TU-R will respond to the loop up codes by
activating the NIU loopback from either the disarmed
or armed state. The loop down codes will return the
H2TU-R to the state from the armed or loop up state.
Refer to Appendix A for more details on loopbacks
and loopback arming sequences.
Figure 3 illustrates all of the possible loopback
locations of the ADTRAN HDSL2 equipment.
Customer Loopbacks
In addition to the loopbacks in the direction of the
network, the H2TU-R may also be looped back in the
direction of the customer. The H2TU-C and H2TU-R
Customer Side Loopbacks are illustrated in Figure 3.
NOTE
Network and customer loopbacks are governed
by the loopback time out option (Default=120
minutes).
5