Prism
Operation Manual Issue 2.00
Page 8.9
the DSA-1 are the PRS-H (wideband noise) function and the fs/8 function. The latter
is significantly reduced only by equipment which attenuates jitter within the audio band.
If the carrier phase-shift through the equipment under test exceeds 25%, the
'BLOCK/PHASE' LED on the DSA-1 is lit. To measure the carrier phase shift directly,
it is necessary to lock the input to the test equipment to a separate reference which is
also connected to the DSA-1 Ref Sync input. The phase can then be measured in the
'Phase-v-Ref' sub-menu, with the DSA-1 generator off.
The data integrity of a suspect equipment or cascade can be monitored using the
DSA-1 'Channel Check' mode, if the data can be passed through unprocessed.
Channel Check mode tests the correctness of every bit of every audio sample for as
long as required. This mode can also be used to check digital audio recorders by
recording the test pattern prior to running the Channel Check. Although this is strictly
a data test, intermittent data errors are usually caused by a marginal carrier.
8.4.2.
'In-line' data tests
By using GEN1 instead of GEN2 in the above setup, it is possible to test aspects of
data transparency.
Channel Status transparency is often an important system issue, since a lot of
equipment, whilst generating its own Channel Status output, is not adequately
transparent to Channel Status from its input. Thus Channel Status applied by a system
source is often destroyed by a subsequent device. GEN1 allows the Channel Status
fields to be defined individually, and the 'C-S Fields' sub-menu in 'Data Tests' allows
the returned fields to be examined.
The SCMS operation of a consumer recorder can be tested by setting the various
SCMS states in GEN1, recording the data, and monitoring the returned SCMS status
on playback. The DSA-1 displays the following SCMS states in its 'C-S Fields' sub-
menu:
SCMS:Orignl Matl
The category code indicates that the material is from
an original source. DAT ID6 is set to x0.
SCMS:Copy, gen1+
The generation status of the material is 1 or higher,
e.g. it is a home-copy of original material. (DAT ID6
will be set to x1).
SCMS:Copy, gen??
The category code of the material provides no
'generation status'; e.g. signals from some A-D
converters.
