Guralp Systems CD1.1 - Manual (Page 27)

Operator's Guide
The Enable check-box controls whether this instance is to be
automatically started each time the system boots or whether it
should be left to be started manually.
The Delete check-box, if ticked, will cause this instance to be
deleted when the form is submitted.
The Subframe duration field controls the length of
subframes. Ten second subframes are recommended for
seismic recordings but some applications typically use longer
lengths. You can choose between ten and one hundred
seconds, inclusively, in ten second intervals.
The Max clock difference field is used to set the “clock
differential too large” bit (bit 1 of byte 4, the miscellaneous
status byte) in the CD1.1 channel subframe status block . If,
for example, a DM24 digitiser loses its GPS signal, it will use a
worst-case drift value to estimate the maximum difference
between its internal clock, now free-running, and GPS time, and
report this difference in its state-of-health information. The
converter will monitor this value and, should it exceed the
value set in this field, it will flag the resulting subframes to
indicate that the time-stamp can no longer be trusted. The
value is specified in microseconds.
The Subframe transformation drop-down menu controls
whether generated subframes are compressed and/or digitally
signed. The choices are:
•
None. Samples are not compress and the subframe is
not signed.
•
Compressed. Samples are coded with Canadian
compression.
•
Signed. Samples are no compressed. The subframe is
signed.
•
Compressed then signed. The subframes are
compressed, then the subframe signed.
The Authentication key ID field sets a flag in the CD1.1
header which some customers use to identify which encryption
key pair (from a pre-defined set) has been used. It is generally
set to be the serial number of the signing certificate. It should
be set to zero if frames are not to be signed.
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