VeEX VePAL TX300M, User Manual

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11.0 PDH Tools
Accessing PDH Tools
On the TX300, tap on Home (main menu) >
Advanced Mode
>
PDH Tools
On the TX300e, tap on Home (main menu) >
PDH Tools
PDH Menu
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11.1 E1 Pulse Mask
This function captures and analyzes E1 (2.048Mbps) pulse shape. The purpose of maintaining the correct pulse shape is to
reduce inter-symbol interference – if the logic 1s and 0s cannot be detected by the receiver correctly, bit and code errors will
result.
The pulse amplitude and overall shape are superimposed and compared with the ITU-T G.703 pulse conformance template.
Telecommunications signals require specific load impedance for pulse mask compliance testing to be accurate. When high
frequency pulses are transmitted down a transmission line, a portion of the pulse will be reflected when and wherever it
encounters an impedance mismatch. The reflection is proportional to the impedance mismatch (i.e., the greater the mismatch, the
greater the reflection of the pulse). To avoid reflections impacting the E1 measurement, the TX300/e will terminate twisted pair
cables with 120 ohms and coax cable with 75 ohms impedance. Note that 75 Ohm and 120 Ohm twisted pair cables each have
different nominal amplitudes associated with them; for the 75 Ohm coax cable, the pulse amplitude must be 2.37V ± 10% while
for 120 Ohm twisted pair cables, the pulse amplitude must be 3.0V ± 10%.
According to the G.703 recommendation, E1 pulses need only be measured at the transmitter output, and are
not
required to
meet the pulse template over a variety of cable lengths. This of course will not provide information on distortions caused by
misalignment and other impairments of the line. The TX300/e on the other hand can connect to a live system at the TX output
port via a Protected Monitoring Point (PMP) or at the far-end of a transmission line. In either case, the signal will be attenuated or
amplified as necessary to compensate for test point or cable attenuation characteristics.
E1 Pulse Mask
TX300S_e-manual_D07-00-064P_RevA00