the self-test, performed after power-up, only tests the internal electric components excluding interfaces.

    3.1 dut installation and test environment

    reference installation chapter of the user's manual.

    3.2 power up

    reference maintenance chapter of the user's manual. for loop-u 3500 stand alone, turn power on and observe the power-up sequence. the lcd screen on the front panel first displays"test..." and if successful, followed by"pass" and the main menu. for loop-u 3500 rack card, when each of loop-u plug-in card is powered up, a complete self-test routine is running. the progress of the selftest is indicated by the leds. if no error is found, the power led will be steady green.

    3.3 dut configuration

    before starting test, the dut must be configured for the test. the configuration can be done by using the front panel lcd and key pads, or using a vt100 type of terminal plugged into the console port in the front panel. note that, for the rack version of the dut, configuration can also be done through the ethernet port. this is beyond the scope of this testing manual is covered under the c5500 interface testing manual.

    3.3.1 dut mode

    for each pair of connected loop-u, one must be lt and the other is nt. the nt mode loop-u can only be synchronized to the lt through the line.

    3.3.2 clock source

    first the clock source is set to internal for lt mode one, and set to line for nt mode one.

    3.3.3 dte parameters

    the dte parameters are set to factory default.

    3.3.4 setup using front panel lcd keys

    the above configuration parameters can be set using the front panel lcd and key pads. refer to"front panel menu tree" of the user's manual. use arrow key to select a tree branch. use the enter key to descend to a branch or select a parameter. use the esc key to ascend the tree.

    3.3.5 setup using terminal

    with the terminal connected and displaying the main menu, press the s key for system setup.(press o if the right hand half of the screen is blank. the default password is"loop".) then use the arrow key to move the cursor to the parameters to be changed and use the tab key to roll to the desired parameter setting. when done , press esc key to return to the main menu.

    3.3.6 synchronization

    after the setup , with the line connected (figure 1), the"sync" will light up ( about 20-30 seconds).

    3.4 bit error test

    after configuration setup , a"bit error test" is performed to verify proper operation.

    the test can be initialed either from the front panel lcd and keypad or attached vt100 terminal.

    3.4.1 test using front panel lcd and keys

    the bit error test is initiated by sending prbs ( pseudo random bit stream) pattern to the line port and back. the results are checked for errors. the test can be started by using the front panel lcd and key pads. refer to "front panel menu tree" of the user's manual. use the arrow key to select a tree branch. use the enter key to descend to a branch or select a parameter. use the esc key to ascend the tree.

    (a) from the main menu , showing diagnostics is displayed. press enter.

    (b) nt mode one selects"near loopback" and press enter. press right or left arrow key until" payload" is displayed. press enter.

    (c) lt mode one selects"bert" and press enter. press right or left arrow key until"full" is displayed. press enter.

    the test will now be in progress.

    3.4.2 test using terminal

    with the terminal connected (lt) and displaying the main menu, press the"t" key for loopback tests. then use the arrow key to move the cursor to remote loopback(2b+d). press enter. then move the cursor to bert(full) and press enter. the test will now be in progress.

    3.4.3 test result

    leave the test on at least for 2 minutes. if the bit error display =0,then the line port both are normal and working. proceed to test 2.else ,unsync or non-zero error will be displayed to indicate line port failed.

    for the front panel lcd, the display would be bert full sync,bit error = 0

    for the vt100,the display would be

    bert sync

    channel = full

    bit error count = 0

    error seconds = 0

    elapsed seconds = xx