Section 311-580-20B
030-101527 Rev. B
7
0407IBRB
4.6.2
To loop back the unit when it is configured for
addressed loopback operation, the test person first sends the in-
band or ESF Data Link Loop-Up command (see Table 1) for the
proper duration. This will loop up the distant NIU and serve as
an arming code for the 3115-80. When the unit is armed, the LB
LED will flash yellow.
4.6.3
The test person then sends the 16-bit repeating pattern
1101 0011 1101 0011 for five seconds minimum. Upon receiving
the code, the unit enters loopback and 10 seconds later returns
an acknowledgement of 232 bit errors indicating the NIU is
looped.
4.7
Manual Loopback
The NIU loopback state can be controlled by pressing the front-
panel MAN LB push button. Depression of the MAN LB push
button will cycle through the loopback states.
When first depressed, the LB LED will go off and remain
off during the first 3 seconds that the MAN LB is depressed.
If released during this 3 second period, all existing loopback
conditions will be deactivated.
If depressed for 3 to 5 seconds, the LB LED will be on solid
(yellow). If released in this interval, the Network Loopback
will be activated.
If depressed for greater than 5 seconds, the LB LED will be-
gin blinking (yellow). If released after 5 seconds, the Dual
Loopback will be activated.
4.8
Loopback Timeout
4.8.1
The unit provides a timeout feature that can be config-
ured to release a code-activated loopback condition either 20,
60, 120 or 1440 minutes (24 hours) after initial activation.
4.8.2
The loopback condition can be released before the
timeout expiration period by: 1) sending loop-down code to the
NIU from the network test location, 2) through the craft inter-
face port, or 3) by pressing the front-panel MAN LB switch for
less than 3 seconds. Loopback timeout can be permanently dis-
abled via an option provisioned locally from the craft interface
port or remotely from the network test location.
4.9
CPE (Dual) Loopback Activation
4.9.1
To activate CPE loopback, the unit must first be in net-
work-side loopback from the remote test location. At this point,
re-application of loop-up code will operate CPE loopback allow-
ing the customer or craft personnel to evaluate the integrity of
the circuitry on the CPE-side of the demarcation point. The unit
can be placed in CPE loopback via the front-panel MAN LB
push button (see Paragraph 4.7). CPE Loopback can also be ac-
tivated and deactivated from the Circuit Status Menu via the
craft interface port.
4.9.2
When CPE loopback is activated, it will remain acti-
vated until:
1.
the NIU detects a loop-down command from the Network-
side,
2.
when the timeout release feature expires,
3.
when released via the craft interface port, or
4.
when the MAN LB switch is pressed for > 5 seconds.
5.
SECTIONALIZATION ALARM FEATURES
The NIU
is equipped with features that allow a network moni-
toring location to differentiate between fault conditions that are
beyond the NIU (i.e., CPE or inside wiring) and those that are
legitimate network problems.
5.1
CPE LOS Modes
5.1.1
LB Upon CPE LOS
In this mode, the unit continuously monitors the DS1 signal
from the CPE for customer loss of signal, and upon detecting a
loss will change the CLOS LED from green to red and cause the
unit to enter Loopback toward the network. When the signal
from the CPE is restored the unit will return to normal opera-
tion. LB upon CPE LOS is an option that can be set remotely via
TL1 or 16-bit commands or locally via the craft interface port.
When set to enter loopback upon detecting a loss of signal from
the CPE, the NIU will assume the transmission path as shown in
Figure 6.
5.1.2
AIS Upon CPE LOS
In this mode, the unit continuously monitors the DS1 signal
from the CPE for customer loss of signal, and upon detecting a
loss will change the CLOS LED from green to red and send an
unframed, all-ones Alarm Indication Signal (AIS) to the net-
work. When the signal from the CPE is restored the unit will
return to normal operation. The AIS upon CPE LOS mode is an
option that can be set remotely via TL1 or 16-bit commands or
locally via the craft interface port.
5.1.3
Idle Code Upon CPE LOS
In this mode, the unit continuously monitors the DS1 signal
from the CPE for customer loss of signal and upon detecting a
loss will change the CLOS LED from green to red and send an
Idle code toward the network. When signal from the customer
is restored, the NIU returns to normal operation. The specific
format in which the Idle signal is sent toward the network facility
is dependent on the format of the DS1 signal received from the
network facility:
1.
If the received signal is SF, the Idle signal will be SF and will
provide a 0001 0111 repeating pattern in each of the 24 DS0
time slots,
2.
If the received signal is ESF, the Idle signal will be ESF and
provide a 0001 0111 repeating pattern in each of the 24 DS0
time slots. In addition, the ESF Data Link will contain the
ESF yellow alarm signal 1111 1111 0000 0000, interrupted
each second with a 100ms burst of LAPD idle code 0111
1110,
3.
If no signal is received from the network or if the DS1 signal
is unframed, the NIU will default to the SF Idle mode.
The Idle Code upon CPE LOS mode is an option that can be set
remotely or locally via TL1 or 16-bit commands or via the craft
interface port.
5.2
CPE Loss Of Signal Override
5.2.1
When the NIU detects a loss of signal from the CPE
and if the CPE Loss of Signal option is enabled, the NIU will re-
spond in accordance to the setting of the CPE LOS option.
These options are as follows:
