Guralp Systems CMG-DCM build <10,000 - Manual (Page 123)

Acquisition Modules and Platinum Firmware Digitiser Synchronisation
Note: Where GPS is available, you should always synchronise the
EAM to the digitiser's RTSTATUS packets rather than directly to
GPS, as explained in section 9.1 on page 120.
The data flow when a GPS receiver is used is illustrated below:
If required, the NTP subsystem can provide NMEA output via a serial port
which can then be used to synchronise an additional digitiser. This, however,
is optional and no serial port is dedicated to this use.
To configure the NTP subsystem, see section 7.4 on page 84.
To configure NMEA as an NTP clock source, see section 9.6 on page 124.
To configure NMEA output, see section 9.7 on page 125.
9.5 Using NTP with Cylindrical Digitisers
Note: Where GPS is available, you should always synchronise the
EAM to GPS, via the digitiser's RTSTATUS packets, rather than to
NTP.
Please see the discussion of synchronisation options available with
Cylindrical Digitisers in the previous section.
MAN-EAM-0003 123 Issue E - February 2014