Verilink 1558A (34-00228) Product Manual - Manual (Page 33)

1558A APS 4-10 LAPS Operation
4.8 Loopback Operations
The 1558A has several loops that can be initiated by the user
to assist in trouble shooting T1 transmission path problems
(see the Block Diagram in
Figure 4-2 ). It is important to
note that the types of loops that a 1558A unit can send or
respond too is dependent upon the manual unit option set-
tings (master/slave). It is also important to note that APS
service must be installed in pairs, one configured as the
master and the other as the slave. In addition, each APS pair
must be configured to operate in either the normal mode or
in the transparent mode. The normal mode allows the slave
unit to respond to CSU loop commands and 54016 com-
mands. The transparent mode disables all CSU functions of
the slave unit.
In most applications, APS service is provided by an IXC. In
these applications, the APS equipment located in the central
office will always be configured for Master/Normal and the
APS equipment located at the customer’s premise will be
configured for Slave/Normal.
The loop types that LAPS can initiate from the front panel
SUPV port of a unit configured as a Master are:
• CO Payload Loop
• CO Line Loop
• Co Facility Loop
• CO Equipment Loop
• NPC Payload Loop (Transparent mode only)
• CPE Payload
• CPE Line
• CSU Loop
• NET Loop (Telco network interface)
The loop types that LAPS can initiate from the front panel
SUPV port of a unit configured as a Slave are:
• Local Facility Loop
• Local Equipment Loop
Before performing loops and unloops, it is important to
understand that the user must carefully set up and select the
desired loopback. It is recommended that the user follow the
steps listed below when setting up a loopback.
1) From the Main Menu, select the Maintenance screen
2) From the Maintenance screen, decide which Path is to
be looped (A or B).
3) If necessary, force the 1558A to use the Path (A or B)
that is not to be looped.
4) Lock this Path (A or B). This prevents the 1558A from
switching the active line to the test line during testing.
Caution: The LAPS software and 1558A hardware will
not allow a user to loop an active line or BERT an active
line. Only a line shown in the Standby mode or Inhibited
mode can be looped or BERT tested.
5) Initiate the desired local/remote loop.
The following sections describe in detail how to perform
loops and unloops of the 1558A equipment. Note that all
loops and unloops are performed at the Maintenance screen.
The location of the various loops is depicted in the 1558A
Block Diagram shown in
Figure 4-2 on page 4-11 . The
remainder of this chapter discusses these loops. Reference to
this block diagram may provide clarification.
4.8.1 Near CO Payload Loop
Target the path (A or B) that you want to test by moving the
cursor highlight to the Target field and then, using the space
bar, toggle the field until it displays the to side that you want
to loop (Side A or Side B). After you have selected either
the A or B side as the target for testing, move the cursor
highlight to the Loop field and toggle the field, using the
space bar, until the field displays CO Payload. Then
momentarily depress the <return/enter> key. The LAPS will
initiate a payload loop of the selected target. After a few
moments, notice that the NEAR status field has changed
from Soft Inhibit or Standby to PL LP. Also note that the
near 1558A front panel Loop LED indicator is on.
A payload loopback loops the incoming T1 signal back to
the network. The T1 signal is regenerated (both CRC and
signal level). In addition to looping the signal back to the
network, the signal is also passed to the 1558A DTE port.
To unloop the unit, move the cursor highlight to the Unloop
field and toggle the field, using the space bar, until CO Pay-
load is displayed. Then depress the <return/enter> key. The
LAPS will issue a payload unloop command. After a few
moments note that the NEAR status field changes from PL
LB to Soft Inhibit or Standby. Also note that the LP LED
indicator on the 1558A turns off. The CO Payload loop is
now off.
4.8.2 CO Line Loop
Target the path (A or B) that you want to test by moving the
cursor highlight to the Target field and then, using the space
bar, toggle the field until it displays the to side that you want
to loop (Side A or Side B). After you have selected either
the A or B side as the target for testing, move the cursor
highlight to the Loop field and toggle the field, using the
space bar, until the field displays CO Line. Then momen-
tarily depress the <return/enter> key. The LAPS will initiate
a CO Line loop of the selected target. After a few moments,
notice that the NEAR status field has changed from Soft
Inhibit to Line LP. Also note that the 1558A front panel
Loop LED indicator is on.