Nortel Networks DCT1900 manual Transmitted and Reflected Pulses

Technical Product Manual - DCT1900

Installation Instructions, Use of TDR

10.A waveform similar to the one shown in Figure 25-1 should be displayed, however the vertical pulse will be located at the left edge of the screen. This is the transmitted pulse the TDR uses to determine the length of the cable.

11.Rotate the horizontal POSITION control (10) until the vertical line it controls is all the way against the left edge of the screen. At this point, the upper right corner of the display should show either 0.00 ft. or some negative value.

12.Connect the pair to be measured to the test cable using the alligator clips. At this point the pair should not be connected to either the base station or the radio exchange, and should be left open-circuited at the far end. Adjust the DIST/DIV control (5) until the display shows not only the transmitted pulse on the left (as in Figure 25-1) but also the reflected pulse farther to the right. This pulse should have the same polarity (positive) as the transmitted pulse. It may be necessary to adjust the Vertical Scale (4) control and/or the Pulse Width control (8) so that the transmitted and reflected pulses are clearly defined and separated as in Figure 25-2.

Figure 24-2 Transmitted and Reflected Pulses

Now, adjust the horizontal Position control (10) until the vertical line it controls is exactly at the leading edge of the reflected pulse. At this point, have someone short the pair at the far end while observing the display. The reflected pulse should invert as the pair is shorted. If not, the pair may be open at some point or you may be testing the wrong pair. Correct the condition and retest until the proper result is obtained.

Have the person at the far end remove the short and observe that the reflected pulse returns to positive polarity and that it is still aligned with the vertical line. If the pulse has shifted, this is an indication that the pair may be open on one side. Correct the condition and retest until the proper result is obtained.

Note the indication in the upper right corner of the display, indicated in feet. Multiply this indicated length in feet by the constant .001025 microseconds/foot. This will yield the delay of the pair in microseconds.

Example: Assume a reading of 167.7 ft. 167.7 ft. x .001025 = .17189 microseconds

Record the calculated delay in microseconds. This value will be used to determine the proper value to enter when adding a Remote Base Station using the Cordless System Manager software for windows.

As the system allows entries only in increments of 0.1, it will be necessary to round.

25-2	Install-DCT1900/R8/mw
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