Verilink 1558D (34-00255) Product Manual - Manual (Page 37)

LAPS Operation 4-11 1558D APS CSU/DSU
To unloop the unit, move the cursor highlight to the Unloop
field and toggle the field, using the space bar, until Near
Payload is displayed. Then depress the <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 1558D turns off. The Payload loop is now
off.
Near 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 Near Line. Then momen-
tarily depress the <enter> key. The LAPS will initiate a Near
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 1558D front panel Loop LED
indicator is on.
A Line loopback loops the incoming T1 signal from the
facility back to the network. Only the T1 signal level is
regenerated, not the CRC. In addition to looping the signal
back to the network, the signal is also passed to the 1558D
DTE port.
To unloop the unit, simply move the cursor highlight to the
Unloop field and toggle the field, using the space bar, until
Near Line is displayed. Then depress the <enter> key. The
LAPS will issue a line unloop command. After a few
moments note that the NEAR status field changes from Ln
Lp to Soft Inhibit or StandBy. Also note that the LP LED
indicator on the 1558D turns off. The Line loop is now off.
Near Facility 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 spa-
cebar, 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 cur-
sor highlight to the Loop field and toggle the field, using the
space bar, until the field displays Near Facility. Then
momentarily depress the <enter> key. The LAPS will ini-
tiate a Near Facility loop of the selected target. After a few
moments, notice that the NEAR status field has changed
from Soft Inhibit or StandBy to Fac LP. Also note that the
1558D front panel Loop LED indicator is on.
A facility loopback loops the outgoing T1 signal back to the
1558D receive. The T1 signal level is regenerated and,
depending on the user option (regenerate CRC yes/no), the
CRC will or will not be regenerated. In addition to looping
the signal back to the 1558D receive, the signal is also trans-
mitted to the network (see the block diagram in Figure 4-10).
To unloop the unit, simply move the cursor highlight to the
Unloop field and toggle the field, using the space bar, until
Near Facility is displayed. Then depress the <enter> key.
The LAPS will issue a line unloop command. After a few
moments note that the NEAR status field changes from Fac
Lp to Soft Inhibit or Standby. Also note that the LP indicator
on the unit turns off. The Line loop is now off.
Near Equipment Loop
A DTE equipment loopback loops the incoming T1 signal
coming into the DTE (Tx) port back to the DTE port (Rx).
Only the T1 signal level is regenerated, not the CRC. In
addition to looping the signal back to the DTE port, the sig-
nal is also transmitted to the network.
To initiate a CO Equipment 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 Near Equipment. Then momentarily depress the
<enter> key. The LAPS will respond by sending the follow-
ing message to the user, “Warning! This loop disrupts
active service. Perform Loop? (Y/N).” If the user enters y
(yes), the system will initiate a DTE Equipment loop. After
a few moments, notice that the NEAR status fields for both
the A and B circuits has changed from Soft Inhibit or
StandBy to Eq Lp. Also note that the 1558D front panel
DTE Loop LED indicator is on. If the user enters N (no)
when prompted with the warning message, the LAPS sys-
tem ignores the equipment loop command.
To unloop the unit, simply move the cursor highlight to the
Unloop field and toggle the field, using the space bar, until
Near Equipment is displayed. Then depress the <enter> key.
The LAPS will issue an Equipment unloop command. After
a few moments note that the NEAR status field changes
from Eq Lp to Soft Inhibit or StandBy. Also note that the LP
LED indicator on the 1558D turns off. The Equipment loop
is now off.
Far Payload
A Far Payload loopback is used to loop the far slave 1558D
unit from the master unit. At the far slave unit, the Payload
loopback loops the incoming T1 signal (RX) coming from
the network (NET A or NET B) port back to the network
(TX, NET A or NET B). Both the signal and CRC are
regenerated. In addition to looping the signal back to the
network, the signal is also transmitted to the DTE port.
To initiate a Far 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