VeEX VePal TX130M+, Руководство пользователя

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21.0 E1/E3 Tools
The E1 and E3 Tools can be found on the main menu. Tap the E1 and E3 Tools icon to display the shortcut screen shown
below.
E1 Tools Menu E3 Tools Menu
E1/E3 Pulse Mask
E1 APS Service Disruption Testing
E1 Frame Words
Round Trip Delay
E1 Rx Data
E1 VF
Jitter Measurement
Wander Measurements
Setup
Results
V.54
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21.1 E1/E3 Pulse Mask
This function captures and analyzes E1 (2,048Mbits/s) or E3 (34,368Mbits/s) 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 will terminate twisted pair
cables with 120 ohms and coax cable with 75 ohms impedance. Note that 75ohm and 120ohm twisted pair cables each have
different nominal amplitudes associated with them - For the 75ohm coax cable, the pulse amplitude must be 2.37V ± 10% while
for 120ohm 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 allows you to 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
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