Guralp Systems CMG-DCM build <10,000 - Manual (Page 17)

Acquisition Modules and Platinum Firmware Equipment Overview
If the output link is over a network, all external serial ports of a standard
CMG-EAM (including the “DATA OUT” port) are available for connection to
digitisers or digital instruments, allowing up to eighteen channels to be
aggregated. An arbitrary number of CMG-EAMs may be chained together,
allowing for even more extensive arrangements.
2.6.4 PPP Networking
A serial output from the CMG-EAM can be used for point-to-point protocol
(PPP) networking. This protocol allows full internet access to the device over
a serial link. Operators can access the web page of the acquisition module for
configuration and monitoring. If other Ethernet devices are present at the
deployment site, the CMG-EAM can function as a router, passing their traffic
over the PPP link. The output from other serial devices can also be passed
over the PPP link by use of the built-in serial-to-TCP converter (see section 7.8
on page 97 for details).
2.6.5 Resilient Networking
Platinum firmware includes a number of ways to implement network
resilience. For example, the GSTM protocol (for communication between
Platinum units) allows data to be routed over a low-cost but unreliable DSL
network with automatic switch-over to a higher-cost satellite link only when
the DSL network is unavailable. The failed link is regularly re-tried and,
when communication is re-established, the data are re-routed back to the
lower cost link.
The CMG-NAM acquires data from Scream servers (e.g. CMG-6TD or
CMG-3ESPCDE) and the data are stored locally on an optional RAID disk
array with up to 2 TB capacity.
MAN-EAM-0003 17 Issue E - February 2014