Section 150-231-134
Revision 01
Page 14
10.05
A2LB through A5LB are four special
addressable repeater loopback functions
which are supported by the List 6 version of HiGain.
These loopbacks provide HiGain with sophisticated
maintenance and trouble shooting tools. Tables 6 thru
9 list the details of these Special Loopback (SPLB)
functions. A2LB & A5LB are patterned after the
Teltrend addressable T-1 repeater loopbacks. A3LB &
A4LB are patterned after the Wescom addressable T-
1 repeater loopbacks. All four SPLBs have been
enhanced to handle the specific requirements of the
following HiGain customers:
A2LB (Teltrend) = Southwestern Bell (default setting)
A3LB (Wescom)=New England Tel.
A4LB (Wescom Mod 1) =New York Tel.
A5LB (Teltrend Mod 1) =Southern New England Tel.
(SNET)
10.06
A5LB differs from A2LB in that A5LB does not
block the arming code from exiting the HLU
into the network. A2LB can be configured to either
block this arming code after 2 seconds, and replace it
with the AIS code, or to unblock it by executing the
FAR-END ACTIVATE code. Since A5LB never
blocks the arming code from exiting the HLU, it does
not need this FAR-END ACTIVATE code. A3LB
differs from A4LB in that A3LB supports the
additional 1 in 6 SmartJack loopback command.
10.07
Two additional loopback points are added for
each HDU-451 doubler that is used as shown
in Figure 6. NDU1 and NDU2 are executed towards
the network. CDU1 and CDU2 are towards the
customer. All four loopbacks can be initiated by the 16
bit in-band commands in SPLB states A1LB, A2LB &
A3LB as described in Tables 3, 4 & 7 respectively.
NDU1 and NDU2, along with the rest of the
loopbacks towards the network, can be issued form
the Loopback Menu shown in Figure 15. See
paragraph 10.09 for front panel- initiated loopbacks.
The simplest HiGain system includes two loopback
locations: The HLU and the HRU. The most complex
HiGain application includes the HLU, HRU & two in-
line HDU-451 doublers. Refer to the PairGain HiGain
Intelligent Repeater Application Note # 910 Part #
325-910-100 for more SPLB details.
10.08
HiGain may take longer than normal to
respond to inband loopback commands when
its framing mode is set to UNFR and the inband
commands are sent in either an SF or ESF mode. The
frame bits override the command bits and cause
errors in the command sequence. These errors cause
HiGain to reject some sequences. This can extend the
detection interval.
10.09
Depressing both the MODE and SEL
pushbuttons on the front panel for at least
three seconds initiates a MANUAL loopback session.
This session allows the user to SEL one of eight
HiGain loopbacks. The message, MAN LPBK,
appears on the front panel display followed by the
message NLO?. If the SEL button is now pressed, an
NLOC loopback is executed and the message
changes from NLO? to NLOC. If the MODE button is
pressed instead of the SEL button, NLO? is replaced
by ND1?. This now allows an NDU1 loopback to be
executed (if it is a doubler application) with the SEL
button. If it is not a doubler application, NRE? follows
NLO?. If this same routine is followed, all eight
loopbacks (NLOC, NDU1, NDU2, NREM, CLOC,
CDU2, CDU1 & CREM) are presented and can be
initiated in the sequence listed. Note that NDU1,
NDU2, CDU1 & CDU2 only can appear in doubler
applications. Once a loopback is executed, it can be
terminated and the next loopback option presented by
pressing the MODE button. If neither button is
pressed for a period of 30 seconds and no loopback is
in effect, this manual loopback session terminates and
the normal margin displays reappear. If any loopback
is in effect, this 30-second time-out is inhibited. The
active loopback and the manual loopback session
continue until the loopback times out in accordance
with the user LBTO setting. Only one loopback can
exist at any given time. Depressing both buttons,
again for 3 seconds, terminates any active loopback,
ends the MANUAL loopback session and returns the
display to normal. Note that these same loopbacks
can be initiated from RS-232 maintenance port by
choosing the LOOPBACK MODE, option D, from the
main menu. This displays the Loopback Menu, shown
in Figure 15, from which any of the eight loopbacks
can be initiated.
