Verilink 1558D (34-00255) Product Manual - Manual (Page 14)

Installation 2-6 1558D APS CSU/DSU
APS service is different from “normal” point -to -point T1
service. The 1558D APS unit accepts a single source signal
from the attached DTE equipment, verifies signal density,
duplicates the signal, and then transmits it on two T1 lines
(Path A, Transmit and Path B, Transmit). This duplication
and dual transmission is also done at the far-end APS equip-
ment.
In addition to the unique transmitting function performed by
the APS, the unit also performs a unique receiving function.
There are two identical signals being received from two T1
lines by the APS equipment (Path A, Receive and Path B,
Receive). The 1558D constantly monitors both of these lines
for satisfactory signal performance. In the event that the
present active receive line exceeds an alarm value, the APS
will automatically switch the service from the failed receive
path to the standby receive path. The active receive signal is
the path connected to the DTE equipment.
Once a path has declared an alarm condition from Errored
Seconds, Consecutively Severely Errored Seconds, Loss of
Frame, or Loss Of Signal, it will not be available for service
until the Line Availability Timer has determined that the line
is available for service (line has run error free for the user
defined time period, 0 to 900 seconds, user definable). At
that time, the path alarm circuitry will be reset and then the
path will be ready to accept service.
Path A Pre-service Testing
Perform the following test steps to verify that the 1558D can
run error free data from the DTE V.35 port to the NET A
port and back (local loop test). The test setup for performing
this test is depicted in Local 1558D Test Diagram, Path A
and Path B on page 2 -8.
1. Connect a data BERT test set to the DTE V.35 port at the
rear of the 1558D unit. The test set should be configured
to generate a BERT pattern (511, 2047, etc.) at the data
rate set previously by the user (56kb - 1.536Mbps). Also,
the test set clocking should be configured to operate per
the clocking options set in the 1558D (Internal, Exter-
nal). Typically, the 1558D will supply clocking to the
DTE equipment.
2. Manually operate the DTE Loop Switch from the AUTO
position to the LL (Local Loop) position. This manually
loops the data coming from the DTE port back to the
DTE port.
3. Optionally, the user can insert a bantam test cord into the
NET A Bridge jacks (transmit and receive). This places a
metallic loop of the transmit signal of the 1558D back to
the receive of the 1558D.
Verify that there is no connection at the NET A
jack when looping the 1558D at the Tx and Rx
bridge bantam jacks.
4. Manually operate the front panel Path Select Switch to
the (A) position. This forces and locks the unit to Path A.
The following unit status LEDs associated with Path A
testing should be illuminated on the unit:
• Power A or B LED ON (green)
• Status ‘Locked’ LED ON (yellow)
• Status Path Active ‘A’ ON (green)
• The Path Status, Alarm A (red) LED may be ON or OFF
depending on the alarm timer setting (0 to 900 seconds)
configured in the 1558D.
5. The 1558D unit is now looped back to the V.35 DTE port
and the BERT test set should be running in sync and
error free. If not, verify that the test set speed and clock-
ing settings are set to work with the speed and clocking
options configured for the 1558D.
Path B Pre-service Testing
Perform the following test steps to verify that the 1558D can
run error free data from the DTE port to the NET B Port and
back (local loop test). The test setup for performing this test
is depicted in Figure 2-2.
1. Connect a data BERT test set to the DTE V.35 port at the
rear of the 1558D unit. The test set should be configured
to generate a BERT pattern (511, 2047, etc.) at the data
rate set previously by the user (56kb - 1.536Mbps). Also,
the test set clocking should be configured to operate per
the clocking options set in the 1558D (Internal, Exter-
nal). Typically, the 1558D will supply clocking to the
DTE equipment.
2. Manually operate the DTE Loop Switch from the AUTO
position to the LL (Local Loop) position. This manually
loops the data coming from the DTE port back to the
DTE port.
3. Optionally, the user can insert a bantam test cord into the
NET B bantam Bridge jacks (transmit and receive). This
places a metallic loop of the transmit signal of the 1558D
back to the receive of the 1558D.
Verify that there is no connection at the NET B
jack when looping the 1558D at the Tx and Rx
bridge bantam jacks.
4. Manually operate the front panel Path Select Switch to
the (B) position. This forces and locks the unit to Path B.
The following unit status LEDs associated with Path B
testing should be illuminated on the unit:
• Power A or B LED ON (green)
• Status ‘Locked’ LED ON (yellow)
• Status Path Active ‘B’ ON (green)