Guralp Systems CMG-DCM build <10,000 - Manual (Page 193)

Operator's Guide
If an external GPS receiver is used but it is not required to use its data
in the EAM, the service on Port C can be set to “none”.
If use of a GPS receiver is impractical but internet-derived NTP
synchronisation is available, this can be used as the clock source for
both the digitiser module and the acquisition module. By setting the
service on Port C to “NMEA out”, the following connections are
enabled:
Both the digitiser's GPS input and Port C of the acquisition module
must run at 4,800 Baud. This should never be changed. Note that, in
this mode, the external GPS socket is disconnected: it cannot be used
as an output for additional digitisers.
14.2.2 Variable Gain Inputs
The authenticated digitiser is fitted with a programmable gain
differential input amplifier which can be set to ×1, ×2, ×4, ×8, ×16,
×32 or ×64 gain operation.
The gain can be set individually for each input channel, either using
the Platinum web configuration interface or directly from the
digitiser's command line. In either case, the digitiser module must be
re-booted before the new value will take effect.
The gain settings are reported in the status stream at boot time:
ADC #1 Version 760303
ADC o/s nulls 0 0 0 0
4 channel system
Gain Control : E8
Gain settings : Ch#0 *1 Ch#1 *1 Ch#2 *1 Ch#3 *1
November 2010 193