Guralp Systems Scream - Manual (Page 79)

User guide
DSP. The DSP has several filtering-decimation stages, which run one
after the other. Stages which can produce output are called taps. The
Güralp DM24 and CD24 digitiser can both output four taps
simultaneously.
Each configurable tap can be set to a different decimation factor by
choosing values from the drop-down menus on the left. Decimation
factors of 2, 4, 5, 8, and 10 are available. The numbers visible in the
drop-down menu of each tap are the data rates that each of the
possible decimation factors will provide, given the settings of the taps
above it. Only integer (Hz) data rates are allowed: thus, for example, if
one tap produces data at 25 Hz, the only possible further decimation
factor is 5.
To the right of each decimation factor menu is a grid of check-boxes.
These boxes mark which streams of data to generate at each sample
rate. The screen-shot above shows a possible configuration for
6-channel digitiser with two triaxial instruments connected. Every
channel of the digitiser may be output at any tap; currently, all three
axes are being output at Tap 3 (100 Hz).
If you want to change the names used for the channels, click in the
white box containing a Z in the above picture, and type a letter or
number. It will name the channels with a sequence of letters or
numbers beginning with the one you choose (e.g. A, B, C; 2, 3, 4; 9, A,
B), unless you type Z in which case they will revert to Z, N, and E.
Each combination of channel and tap has two check-boxes. The upper
check-box of each pair activates continuous output, whilst the lower
activates triggered output. In the example above, the digitiser will
output data continuously for all six channels at Tap 3, but never for
any other taps. You cannot tick both continuous and triggered output
for the same channel and tap.
When you enable a triggered stream, the digitiser will output data in
that stream only when a particular set of trigger criteria are met. This
is pictured in the window as a switch. For example, to generate
high-rate data from Tap 2 only when an event registers at some other
tap, the lower check-boxes of Tap 1 should be ticked.
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