Diagnostics
4-13
GDC 048R154-000
Network Local Test
The data path for the Network Local Test is illustrated in Figure 4-9.
This test can only be commanded from the terminal interface
Diagnostics Selection screen.
The DSU loops the transmit signal back to the receive path at the
network interface. While the loop is in effect the DSU transmits an
Alarm Indication Signal (all ones) on the T1 line. The DTE interface
remains active so that a test signal can be generated and checked by an
external device.
Local Test checks the local DSU, including the channel interface,
isolated from the T1 line. Error detection and reporting is entirely the
responsibility of the external device that supplies the test signal.
To initiate the loopback from the Diagnostics Selection screen, select
[5] Start Network Local Test
.
Figure 4-9
Data Path for Network Local Test
Network Local Test with QRSS Self Test
The data path for the Network Local Test with QRSS Self Test is
illustrated in Figure 4-10. This test can only be commanded from the
terminal interface Diagnostics Selection screen.
The DSU generates a QRSS test pattern, loops the transmit signal back
to the receive path at the network interface, and checks the returned
test pattern for errors. While the loop is in effect the DSU transmits an
Alarm Indication Signal (all ones) on the T1 line. The DSU is
electronically disconnected from its DTE during the test.
DeskTop T1 DSU
DTE
Interface
Network
Interface
DTE or
other
signal
source