LAPS Operation
4 -13
1558A APS
back to Soft Inhibit or Standby. Also note that the Loop
LED indicator on the far slave 1558A turns off. The CPE
Line loop is now off.
4.8.7
CSU Loop
The 1558A, when configured as a Slave unit with the CSU
mode Enabled, will respond to industry standard CSU loop
and unloop commands. A CSU loopback loops the incoming
T1 signal (RX) coming from the network (NET A or NET
B) back to the network (TX). Only the signal is regenerated
by a CSU loop. In addition to looping the signal back to the
network, the signal is also transmitted to the DTE port.
To initiate a CSU loop, first target the path (A or B) that you
want to test by moving the cursor highlight to the Target:
field and then, using the spacebar, toggle the field until it
displays the 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
CSU. Then momentarily depress the <return/enter> key. The
LAPS will respond by sending the appropriate loop com-
mand to the far end slave unit. After several seconds, notice
that the FAR status field has changed from Soft Inhibit or
Standby to Loop. Also note that the far end slave 1558A
front panel Loop LED indicator is on.
To unloop the unit, simply move the cursor highlight to the
Unloop field and toggle the field, using the space bar, until
CSU is displayed. Then depress the <return/enter> key. The
LAPS will issue an unloop command. After several seconds,
note that the FAR status field changes from Loop to Soft
Inhibit or Standby. Also note that the Loop LED indicator
on the far slave 1558A turns off. The CSU loop is now off.
4.8.8
NET Loop
The NET loop command is used to generate 5-bit patterns
towards the far end equipment. These patterns may be used
to loop a network interface device or a CSU. To initiate a 5-
bit NET pattern, first target the path (A or B) that you want
to test by moving the cursor highlight to the Target: field
and then, using the spacebar, toggle the field until it displays
the 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 NET. Note
that when the NET command is selected, a user definable 5-
bit code field is also displayed [10000]. This 5-bit field can
be set to any combination of ones and zeros by moving the
cursor highlight to this field and then entering the desired
combination of ones and zeros at the message prompt.
The most common network interface loop up 5-bit pattern is
[11000]. The most common unloop 5-bit pattern for network
interface devices is [11100]. After selecting the 5-bit pat-
tern, move the cursor back to the Loop field and press the
<return> key. The LAPS responds by sending the selected
NET 5-bit code to the far end equipment for 5 seconds or
more.
To unloop the network interface device, simply move the
cursor to the Unloop field and toggle it with the spacebar,
until NET is displayed. Note that when the NET command
is selected, a user definable 5-bit code is displayed [11100].
This field may be set to any combination of ones and zeros
by entering the desired combination. The most common net-
work interface unloop command is [11100]. After pressing
<return>, the LAPS will issue a NET unloop command for 5
seconds or more, after which, the NET device should be
unlooped.
4.8.9
NPC Payload Loop
The NPC Payload loopback is used to loop a far end slave
unit that is configured to operate in the transparent mode. In
this mode the far end slave card will not respond to any ESF
CSU commands. Normally, this application is used only by
an IXC internal network protection applications. Note that a
NPC Payload loop is functionally the same type as a CPE
Payload loopback.
A NPC Payload loopback is used to loop the slave 1558A
unit from the master unit. At the far end slave unit, the NPC
Payload loopback loops the incoming T1 signal (RX) com-
ing from the network (NET A or NET B) port and loops this
signal back to the network (TX). Both the signal and CRC is
regenerated. In addition to looping the signal back to the
network, the signal is also transmitted to the DTE port.
To initiate a NPC Payload loop, first target the path (A or B)
that you want to test by moving the cursor highlight to the
Target: field and then, using the spacebar, toggle the field
until it displays the 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 NPC Payload. Then momentarily depress the
<return/enter> key. The LAPS will respond by sending the
appropriate loop command to the far slave unit. After a few
moments, notice that the FAR status field has changed from
Soft Inhibit or Standby to PL LP. Also note that the far end
1558A front panel Loop LED indicator is on.
To unloop the unit, simply move the cursor highlight to the
Unloop field and toggle the field, using the space bar, until
NPC Payload is displayed. Then depress the <return/enter>
key. The LAPS will issue an unloop command. After a few
moments note that the FAR status field changes from PL LP
to Soft Inhibit or Standby. Also note that the Loop LED
indicator on the far slave 1558A turns off. The NPC Payload
loop is now off.
