Guralp Systems Scream - Manual (Page 78)

Scream! 4.5
GPS Type : The digitiser needs to be able to time-stamp accurately all
data that passes through it. It can set its clock either by receiving time
signals from the GPS satellite network using an attached
Garmin-compatible (NMEA output) unit, or by taking time information
from a central site (stream sync mode). In stream sync mode, the
digitiser expects to receive two-byte packets from the central timing
source, which may have its own GPS unit, or take signals from one of
the radio time standards. Choose the mode you require from the
drop-down menu.
Enable GPS power cycling : If you are using a GPS unit to receive time
signals, but do not experience significant drift in the system's clock
(for example, in a stable-temperature environment), you can save
power by selecting Enable GPS power cycling. With this option in use,
the GPS time is only checked at intervals of a specified number of
hours. Disabling this option keeps the GPS unit running constantly; if
you have ample power, this will give the most accurate results. You
can choose any whole number of hours for the interval.
7.2 Output control
The Output control tab allows you to configure which data streams are
sent to Scream! from the digitiser.
Güralp digitisers initially sample incoming data at a high rate (e.g.
2000 Hz for the DM24), which is then filtered and reduced to a lower
rate (decimated) using an on-board digital signal processing unit, or
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