Guralp Systems CMG-DM24S12AMS - Manual (Page 21)

CMG-DM24S12AMS Operator's guide
There are two triggering algorithms which Güralp digitisers can use.
However, not all models can use both methods. Scream! will find out
from the digitiser whether its on-board software supports each method.
STA/LTA
The STA/LTA algorithm applies a simple short-term average – long-term
average calculation to the triggering stream. It works by identifying
sections of an incoming data stream when the signal amplitude
increases. The purpose of taking a short term average, rather than
triggering on signal amplitude directly, is to make it less likely that
spurious spikes will trigger the device. Averaging also introduces an
element of frequency selectivity into the triggering process.
You can select which tap is tested for the trigger from the Data source
drop-down menu. The tap does not have to output data to Scream! for
you to be able to use it here.
Any or all of the channels available at that tap may be used to determine
a trigger. You can select which channels are considered by checking the
boxes in the Channel column of the table. If any of the checked channels
passes the trigger condition, the trigger will activate, and will not
detrigger until all of the checked channels have fallen below their
respective ratio values.
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