Guralp Systems CMG-DCM build <10,000 - Manual (Page 83)

Operator's Guide
STA/LTA triggers activate when the ratio of the short-term average to
the long-term average (of the input signal) exceeds a configured value.
The trigger input drop-down menu allows the selection of the input
signal to be used for these calculations, along with one of three filter
settings. The available filters have lower corner frequencies based on
fixed fractions of the sample frequency: specifically, 5%, 15% and 25%
of the sample rate. The upper corner is the Nyquist frequency (half the
sample rate). For example, if a tap configured for 25 samples per
second, the three filters offered will have pass-bands of 1.25Hz to
11.25Hz, 2.5Hz to 11.25Hz and 6.125Hz to 11.25Hz.
The periods over which the short term and long term averages are
computed, along with the triggering ratio itself, can be altered by
changing values in the table. The check-boxes next to each
component are used to enable or disable the use of that component's
output in the STA/LTA triggering algorithm.
Level triggering is controlled by the following dialogue:
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