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DIGITAL LINK MEASURING INSTRUMENTS

Measurement item

Functions

•

Automatic measurement mode

In the automatic measuring mode, voice encode and decode perfor-

mance characteristics can be measured. Encode and decode perfor-

mance characteristics in the voice frequency are recommended in

ITU-T Rec. G712/713/714/792 Q.507. Many items are required for

voice frequency evaluation, and many points must be measured for

each item.

In attenuation/frequency distortion, some compensation of the mea-

surement value is required for each measurement frequency because

of the absolute level difference caused in the reference frequency.

Manual correction requires much time and effort to obtain the correct

result.

The MS371A/A1 stores the reference frequency, the level difference

in the frequency, the subsequent frequency for measurement, and

the procedure for compensation operations at each frequency. As a

result, the corrected result is reached automatically. Then the mea-

sured result is compared to a reference value in the memory to eval-

uate whether or not it passes or fails; evaluation is automatic.

If it fails, the item, condition, and results can be printed out (fail-only

printout or complete printout of results can be selected). In automatic

measurement, the MS371A/A1 can measure the 15 items shows in

the table below, including attenuation/frequency distortion. The mea-

surement table summary indicates whether items can be measured

or not by comparing the measurement configuration with measure-

ment items. Functions that cannot be executed cannot be measured

in principle.

Summary of automatic measurement

Level setting

Measurement configuration

A-A A-D D-A D-D

A-D/D-A

∗

√√√√√

Attenuation frequency distortion

√√√√√

Variation of gain with input level (tone)

√√√√√

Variation of gain with input level (noise)

√√√√√

Total distortion including quantizing distortion (tone)

√√√√√

Total distortion including quantizing distortion (noise)

√√√√√

Idle channel noise

√√√√√

Far-end crosstalk

√

∗

√

∗

√

∗

Near-end crosstalk

√

∗

√

Go-to-return crosstalk √

√

Return loss

√

∗

√

∗

√

∗

√

∗

Spurious out-of-band signal

√√√

Discrimination against out-of-band input signal

√√ √

Longitudinal balance

√√√ √

E&M signalling distortion

√√√√√

∗1: Only when used with channel selector

∗2: Measures D/A immediately after measuring A/D

As an application example, the measurement of PCM terminal voice

encode and decode performance characteristics is shown below.

This measuring method is used when installing PCM terminal equipment.

Measurement items shown in the table of measurement summary are

executed in the measuring sequence programmed into the MS371A/A1.

(The operator can set individual items to be executed or omitted.)

After measurement in channel 1, the MS371A/A1 controls the MS120A

Channel Selector via the GPIB, connects the measuring terminal of

the MS371A/A1 to channel 2 of the PCM terminal equipment, and re-

measures.

Measurement of one system portion of the terminal equipment is finished

from channel 1 to 30 automatically in the same way. Upon completion

of measurement, the measured results of channel 1 to 30 are edited

according to each measurement item and output to the external printer.

As mentioned above, voice channel measurement is fully automated,

with no chance for miss operation.

MS371A/A1

PCM Channel Analyzer

Digital

signal

analyzer

Analog

signal

generator

Digital

signal

generator

Analog

signal

analyzer

GPIB

MS120A

Channel

Selector

30S

30R

30S

30R

Measured PCM

terminal

equipment

PCM S

PCM R

Printer

The MS371A/A1 controls the MS120A Channel Selector via GPIB. Port A scans from 1R to 30R

and port B scans from 1S to 30S. This permits automatic testing of 30 PCM channels (1 system).

Four-wire VF interface PCM terminal equipment automatic testing

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