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2 seedlink – Guralp Systems CMG-DCM User Manual

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CMG-DCM Data Communications Module

your instrumentation whilst minimizing the bandwidth used.

datatransfer.scream.server.coalesce : Some digitizers are configured to

produce GCF blocks at higher than normal rates. This may be done, for
example, to reduce the latency in data transmission. Blocks produced

this way may not all be full, so space will be wasted in the recording
medium.

Selecting this option makes the DCM build full GCF blocks from the

data it receives (a process known as

re-blocking) before transmitting

them.

If you enable

datatransfer.scream.server.coalesce, you will not be able

to connect to the terminal of any connected digitizers using the
Scream! server (

i.e.

the DCM will behave as if

datatransfer.scream.server.allowserialaccess was no.)

You can still configure the digitizers using the Web page (Section 7,
page 105) or using command line tools like minicom and gcli (see

Section 8.2, page 117).

5.2 SeedLink

SeedLink is another member of the SEED / MiniSEED family of
formats, designed for transferring seismic data over a network. The

DCM's slserver package provides a SeedLink server.

SeedLink expects streams to be named using station, channel, and

network codes according to the FSDN SEED naming convention.
Before using the SeedLink server, you will need to define these codes

for every stream you expect to receive. This is done on the Seed name
mappings page (see Section 5.7, page 75.)

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