COMSPHERE 3500 Series Data Service Units3-8 July 1999 3510-A2-GN32-70Digital Test (Point-to-Point)Digital Test is a data disruptive test used to determineif both DSUs and the DDS (Digital Data Service) networkbetween the DSUs are functioning properly (Figure 3-4).Point-to-Point Digital Test OverviewAfter the remote DSU is put in Digital Loopback, thistest uses a test pattern generator that is built into the localDSU. The generator sends a test message over thenetwork to a remote DSU where it is looped back(Figure 3-4). The local DSU passes the received testmessage to the comparator. The comparator checks themessage for errors. Isolated errors cause sporadic flashesof the local DSU front panel FAIL indicator. Steady errorscause the FAIL indicator to flash continuously.The DTE cable for each DSU is not required to beconnected to do this test. However, to do this test, eachDSU must be powered on, connected to the network, andthe network line must be functional. The remote DSUmust be configured to allow remote Digital Loopbacktesting (S1-6 open), or the test will fail.Press the Remote Loopback (RL) and test pattern (TP)test switches to start test at the local DSU. The test doesnot require an attendant at the remote DSU location.When the test is completed, press the RL and TP testswitches to return the DSU to normal.Figure 3-4. Digital Test (Point-to-Point) Diagram
