6
Section 61246026L6-5, Issue 2
61246026L6-5B
6
7
8
9
1
2
3
4
5
TXD (Transmit Data)
RXD (Receive Data)
SGN (Signal Ground)
Finally, the HTU-R responds to T1 Network
Interface Unit (NIU) loopback codes as described in
Bellcore TR-TSY-000312 if the HTU-R is optioned
for NIU loopbacks. The NIU loopback codes are as
follows:
In-band Codes:
Loop up ............ 11000
Loop down ....... 11100
ESF Codes:
Loop up ............ 0001 0010 1111 1111
Loop down ....... 0010 0100 1111 1111
Receiving the in-band codes for more than five
seconds or the ESF codes four consecutive times
will cause the appopriate loopback action.
The Low Voltage HTU-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 HTU-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 4 illustrates all of the possible loopback
locations of the ADTRAN HDSL equipment.
Customer Loopbacks
In addition to the loopbacks in the direction of the
network, the HTU-R may also be looped back in the
direction of the customer using the terminal control
port of the HTU-C or the LOC LBK switch on the
front panel of the HTU-R. The LOC LBK switch
enables a bilateral loopback. The HTU-C can be
looped to the customer using the REM LBK switch
on the front panel of the HTU-R. The HTU-C and
HTU-R Customer Side Loopbacks are illustrated in
Figure 4.
Network and customer loopbacks are
governed by the loopback timeout option
configured on the HTU-C.
5. CONTROL PORT OPERATION
The HTU-C provides a faceplate-mounted DB9
connector that supplies an RS-232 interface for
connection to a controlling terminal. The pinout of
the DB9 is illustrated in Figure 5.
The terminal interface operates at data rates from
1.2 kbps to 19.2 kbps. The asynchronous data
format is fixed at 8 data bits, no parity, and 1 stop
bit. The supported terminal type is VT-100 or
compatible.
Many portable personal computers use
power-saving programs that are known to interfere
with applications running on the personal computer.
If using a portable personal computer with terminal
emulation capability, communication between the
computer and the HDSL unit may be periodically
disrupted if power saving programs are being used
on the personal computer. The symptoms may
include misplaced characters appearing on the
screen and/or the occurrence of screen timeouts.
These symptoms are not disruptive to the operation
of the circuit and are avoidable if the power saving
options are disabled or removed.
Operation
For abbreviations used in the screen diagrams, see
Table E.
The screens illustrated in Figures 6 through 15 apply
to an HDSL circuit deployed with ADTRAN’s Low
Voltage HDSL technology. The circuit includes an
HTU-C, HTU-R, and two HREs. This scenario was
chosen for inclusiveness of functionality; however,
other configurations are possible and their displays
will vary slightly from those shown in this section.
A terminal session will initiate upon plugging into
the front panel interface port. An Introductory
Menu will appear, as illustrated in Figure 6.
From the Introductory Menu, select the Main Menu
by typing “M.” The Main Menu provides access to
detailed performance and configuration information,
as illustrated in Figure 7.
Figure 5. RS-232 (DB9) Pin Assignments
