Guralp Systems Limited
MAN-SWA-0001 Issue M - Scream User's Guide
Section Index: 5.1 The stream buffer 5.2 The source tree 5.3 The stream list 5.4 The status bar 5.5 Viewing streams 5.6 Connecting to instruments 5.7 Calibration data 5.8 Other features

Chapter 5. The Main Window

When you start Scream!, you will be shown an empty Main Window:

This will become populated once you start adding data sources.

The Main Window window is the controlling window for the instance. (It is possible to run many simultaneous instances provided that they have different initialisation files - see section 16.1 for more details.) Scream!'s other windows can be opened and closed as you wish but, if you close the main window, the instance will exit.

Note: See section 15.1 for a list of keyboard shortcuts that you can use in the main window.

5.1 The stream buffer

Scream! works by recording incoming streams into a fixed area of memory, called the stream buffer. All of Scream!'s operations work with the data in this buffer.

(When viewing recorded files, the file itself is used instead of the stream buffer, which allows much larger data-sets to be handled. View mode has a memory overhead of around 10% of the size of the recorded file(s): this is used to store summary information.)

When you start Scream! for the first time, this buffer is empty. You can add data to it either by receiving it from local serial ports, connecting to Scream! network servers, or replaying GCF files.

Once the stream buffer is full, Scream! will start discarding the oldest data. If you have not told Scream! to record the incoming streams (see Chapter 11), then you will not be able to retrieve these discarded data.

Note: You can change the size of the stream buffer from the Display pane of the Setup window (see section 6.4.1).

If you have enabled GCF recording, Scream! keeps track of the files which contain data in the stream buffer, and saves this information in a .lst file in a folder .display.lst under the current recording directory (set using the Base Directory item on the Files tab of the set-up dialogue). When Scream! is restarted, it reads this file and tries to rebuild the stream buffer as it was when it was shut down. Otherwise, the buffer starts off empty as before.

5.2 The source tree

The tree in the left panel of the Main Window shows all the data sources currently connected to Scream!, whether local instruments, networked instruments, or files being replayed.

Scream!'s source tree has two main parts:  Files, which contains all the files you have replayed (including automatic replay: see section 11.2), and  Network, which represents your seismic network.

Beneath Network is a list of all the network servers Scream! is receiving data from, plus the entry Local for your computer's own serial ports, if in use.

The next layer contains the serial ports themselves. These icons are provided to help you identify the instruments, as well as providing direct terminal access.

As an example, the screen shot above shows Scream! running on a computer which is not directly attached to any instruments, although it has a serial port labelled Com1. It receives data from two network sources: An EAM, EAM2243, and a PC, BANFF (which is sending its data via a system called JURAND).

The EAM has two serial ports, Port A and Port B, and BANFF has four serial ports, Com21, Com22, Com24 and Com25. Port A on the EAM is attached to instrument A808-4B15, Port B on the EAM is attached to instrument CD24-B73Q and Com21 on BANFF is attached to three instruments, BHCH3-4910, BHCH4-9669 and BHCH4-5095.

The EAM2243 server icon and the JURAND>BANFF server icon have been “unrolled” to reveal the serial port icons. You can “roll up” icons and save space by clicking on the box. This has been done to Com22, Com24 and Com25, where the box has been replaced by a , which will unroll the sub-tree when clicked.

You can tell Scream! to ignore a particular instrument by right-clicking on its icon and selecting Ignore. When you do this, Scream! will discard any blocks it receives from the instrument. They will not appear in the stream buffer or be recorded to disk. Select Ignore again to stop ignoring the instrument. This setting is not remembered through stop/start of Scream.

Note: See section 15.1.2 for a list of keyboard shortcuts that you can use in the source tree.

5.2.1  Icons

Instrument icons change colour to provide you with a quick overview of the instrument's timing (top half) and mass position (bottom half) status:

If both halves of the instrument icon are grey , Scream! has not received any state of health information from the instrument since the program started.

If the top half is green , the instrument has reported a satisfactory timing fix. Some digitisers might indicate an additional trimmed status with a purple top half, which is better than green. During normal operation, the icon might alternate between green and purple.

If the top half is yellow , the instrument has reported a degraded timing quality. This will occur if the GNSS signal deteriorates to the point where the receiver cannot keep a lock on the satellites.

If the top half is red , the instrument has not reported a satisfactory timing fix for over an hour. This will happen if the instrument has reported failures (as above), but also if it has not reported anything. If you have set the GNSS system to power down for intervals longer than an hour, the icon will turn red even if the system is working normally.

If the bottom half is red , the instrument (or one of its components) is running with a mass position which exceeds a safe threshold. This threshold is set in the EMail tab of the Setup window - see section 13.2 for details. You should re-centre the component, if possible, to avoid clipping during large ground movements.

If the instrument appears as a green box , the instrument has sent status blocks to Scream!, but no data. The box represents a Güralp CRM/SAM; these modules stored or forwarded data from other instruments, but occasionally produced status blocks themselves. If a digitiser produces a status block before any data, perhaps because you have configured very slow data rates, or are using FILING or DUAL transmission modes (see section 10.5), it can appear with this icon temporarily.

5.3 The stream list

If Network is selected in the source tree, the right-hand panel will list all the data streams which Scream! receives (other than those which it is ignoring). If an entry in the source tree is selected, the stream list will only show the streams beneath that entry—selecting a serial port will only show streams from instruments connected to that port, and so on.

The first column contains the Stream ID. The other columns in the table provide useful information about each stream. A System ID and a Stream ID, together, uniquely identify a data stream. The Stream ID is encoded as described below.

Note: See section 15.1.3 for a list of keyboard shortcuts that you can use in the stream list.

5.3.1 Stream IDs

A Stream ID is a unique name for the data stream, being a combination of six letters A – Z and numbers 0 – 9. The first four characters of this name identify the digitiser, and the last two characters identify the individual stream.

The first four characters are set by default to the serial number of the digitiser; you can change this on the System ID pane of the Configuration Setup window (see section 9.1) or from the digitiser's console.

The last two characters tell you the type, component, and output tap of the stream. The possible values for streams from CD24 and DM24 digitisers are given in the table below. The Affinity and Minimus digitisers add many more possible IDs: please see the relevant digitiser manual or the Support→FAQs section of our web site for further details.


Data source

Main outputs (See note 1, below)


SENSOR A, Vertical channel, 1st (fastest) tap


SENSOR A, Vertical channel, 2nd tap


SENSOR A, Vertical channel, 3rd tap


SENSOR A, Vertical channel, 4th (slowest) tap

N0, N2, N4, N6

SENSOR A, North/South channel, 1st to 4th tap, respectively

E0, E2, E4, E6

SENSOR A, East/West channel, 1st to 4th tap, respectively

Mass positions


SENSOR A, Vertical channel, mass position output


SENSOR A, North/South channel, mass position output


SENSOR A, East/West channel, mass position output

Metadata and text streams


The status stream


The contents of the information blocks (only sent at boot-up or on request). See section 5.7 for details.


Byte-pipe data (from text-to-GCF converters)


Unified status (structured state-of-health information)


Structured status for CD1.1 (obsolete)

Second instrument, main outputs (See note 2, below)

Z1, Z3, Z5, Z7

SENSOR B, Vertical channel, 1st to 4th tap, respectively

N1, N3, N5, N7

SENSOR B, North/South channel, 1st to 4th tap, respectively

E1, E3, E5, E7

SENSOR B, East/West channel, 1st to 4th tap, respectively

Auxiliary inputs and calibration returns


SENSOR A, Auxiliary input, 1st (fastest) tap


SENSOR A, Auxiliary input, main output, 2nd tap


SENSOR A, Auxiliary input, main output, 3rd tap


SENSOR A, Auxiliary input, main output, 4th (slowest) tap


SENSOR A, Calibration signal return, 1st (fastest) tap


SENSOR A, Calibration signal return, 2nd tap


SENSOR A, Calibration signal return, 3rd tap


SENSOR A, Calibration signal return, 4th (slowest) tap


SENSOR A, multiplexed input B (used as calibration signal return on early digitisers)


SENSOR A, multiplexed input C


SENSOR A, multiplexed input D


SENSOR A, multiplexed input E (connected to an internal thermometer on some models)


SENSOR A, multiplexed input F

Triggered data


SENSOR A, Vertical channel, triggered output, 1st (fastest) tap


SENSOR A, Vertical channel, triggered output, 2nd tap


SENSOR A, Vertical channel, triggered output, 3rd tap


SENSOR A, Vertical channel, triggered output, 4th (slowest) tap


SENSOR A, North/South channel, triggered output, 1st to 4th tap, respectively


SENSOR A, East/West channel, triggered output, 1st to 4th tap, respectively


SENSOR B, Vertical channel, triggered output, 1st to 4th tap, respectively


SENSOR B, North/South channel, triggered output, 1st to 4th tap, respectively


SENSOR B, East/West channel, triggered output, 1st to 4th tap, respectively


Auxiliary channel, triggered output, 1st to 4th tap, respectively

Strong motion and Causal-filtered (low-latency) data (See note 3, below)


Windowed minimum for Vertical, North/South and East/West, respectively


Windowed minimum for two-dimensional, horizontal resultant


Windowed minimum for three-dimensional (3D) resultant

ZP, NP, EP, 2P, 3P

Windowed PGA for Vertical, North/South, East/West, horizontal resultant and 3D resultant, respectively

ZQ, NQ, EQ, 2Q, 3Q

Windowed maximum for Vertical, North/South, East/West, horizontal resultant and 3D resultant, respectively

ZR, NR, ER, 2R, 3R

Windowed RMS for Vertical, North/South, East/West, horizontal resultant and 3D resultant, respectively

ZS, NS, ES, 2S, 3S

Windowed spectral intensity for Vertical, North/South, East/West, horizontal resultant and 3D resultant, respectively

ZT, NT, ET, 2T, 3T

Windowed average for Vertical, North/South, East/West, horizontal resultant and 3D resultant, respectively


On an S6 digitiser, SENSOR A, Causal-filtered (low-latency) data for Vertical, North/South and East/West, respectively


On an S6 digitiser, SENSOR B, Causal-filtered (low-latency) data for Vertical, North/South and East/West, respectively (See note 2, below)


On an S3 digitiser, Causal-filtered (low-latency) data for Vertical, North/South and East/West, respectively


Scream! can replace these designations with more helpful names if you wish: see section 6.4.2.

5.3.2 Other columns

The other columns of the Stream List are:

5.3.3  Sorting options

Sorting options are available from the ViewSort By menu:

Select the Reversed option to reverse any of these sort orders.

You can also sort the list by Stream ID or SPS by clicking on the relevant heading; click again to reverse the sort order.

5.4 The status bar

At the bottom of Scream!'s Main Window is a status bar containing summary information about Scream!'s state:

To disable or re-enable the status bar, deselect View → Status Bar on the menu.

5.5 Viewing streams

Double-click on one of the streams to open a window for viewing the data, or right-click on it and select View…. Alternatively, make a selection of streams from the list and then either double-click on the selection or key .

The selected data streams are opened in a WaveView window:

This window allows you to see real-time data coming in. You can also pause the window and examine any features held in the stream buffer. For full information on the features provided by WaveView windows, see Chapter 6.

Status streams (ending 00) consist of plain text. Double-clicking on a status stream produces the Status window:

The first blocks transmitted by a digitizer after power-up will give the boot message from the digitiser, including its software revision and the data streams selected for downloading and triggering. Later blocks give information on visible GNSS satellites, the location of the GNSS antenna and time synchronization status. Also displayed are the baud rates currently used for each channel and for the data link.

For more information on status streams and GNSS, see section 8.2.

If you View a selection which includes both status and data streams, the status streams will be collected together and displayed in a tabbed Status window, whilst the data streams will appear in a single WaveView window.

5.6 Connecting to instruments

There are two basic user interface types for the control and configuration of Güralp digitisers:

Some products contain both types of module (e.g. DM24SxEAM), where either interface can be used. However, the interfaces are not universally interchangeable, so the operator should choose to use one or the other, but not to mix both.

This section mainly discusses the interface for the above-mentioned type 1 modules. For type 2 – right-click on the computer icon in the source tree and select Open Web Browser. Under Windows, this will open a web page in your default browser, referencing the sending network address as a URL. Under Linux, the command firefox is invoked with the URL as an argument. See the product-specific documentation for more information on it’s web interface.

Digitiser configuration (and other common operations) for DM24 and CD24 modules can be performed from Scream! by right-clicking on the digitiser in the source tree and selecting Configure… or Control… See Chapter 9 and Chapter 10 for more information.

Scream! also allows you to access the serial terminal of a connected DM24 or CD24 digitiser in order to issue commands directly. To do this, right-click on it and select Terminal…. See section 8.1 for more information about Scream!'s built-in terminal emulator.

An instrument may connected to Scream! through a series of other units (NAMs, EAMs etc). Scream! will negotiate with each unit in turn to reach the instrument you are interested in. However, the process may take a little time.

Right-clicking on a digitiser and selecting Triggers… brings up a window describing all the digitiser triggers that have been detected. This window can also be reached from the Summary window: see section 8.3 for more information.

5.7 Calibration data

Scream! can display data streams from displacement, velocity, and acceleration sensors in physical units. To be able to do this, it needs to know the calibration information provided with the sensor and digitiser.

Newer Güralp digitisers transmit calibration information in an information block (or InfoBlock) when they reboot. When Scream! receives an information block that it understands, it automatically extracts this information and remembers it.

You can also enter and edit calibration information manually. Right-click on the digitiser's icon and select Calvals…. A window will open with a text entry box. This window lets you edit Scream!'s calibration values file.

Fill in the text box with calibration information for your digitiser and the instrument connected to it, in the format described below.


Sensor type code


5T or 5TD, DC – 100 Hz response



40T-1 or 6T-1, 1 s – 100 Hz response



40T-1 or 6T-1, 2 s – 100 Hz response



40T-1 or 6T-1, 10 s – 100 Hz response



40T, 20 s – 50 Hz response



40T, 30 s – 50 Hz response



3T or 3ESP, 30 s – 50 Hz response



40T, 60 s – 50 Hz response



3T or 3ESP, 60 s – 50 Hz response



3T or 3ESP, 100 s – 50 Hz response



3T or 3ESP, 120 s – 50 Hz response



3T, 360 s – 50 Hz response



3TB or 3V / 3ESP borehole,
30 s -  50 Hz response



3TB or 3V / 3ESP borehole,
100 s – 50 Hz response



3TB or 3V / 3ESP borehole,
120 s – 50 Hz response



3TB or 3V / 3ESP borehole,
360 s – 50 Hz response



3TB or 3V / 3ESP borehole,
360 s – 100 Hz response



When you have filled in all the values, click .

Any WaveView windows that are open will change to show streams in physical units. New WaveView windows will also use these units where possible.

Note: If an instance of Scream is receiving data forwarded by another copy of Scream, it will request an InfoBlock from the upstream instance if it receives data from a source for which it has no calibration information.

Note: See the note in section 16.2 for information about possible alternative locations of the calvals.txt file. If multiple calvals.txt files are found, they will appear in the Parameter Data From and Parameter Data To drop-down menus. The displayed values are taken from the file identified in Parameter Data From and the Save button writes the (possibly modified) values to the file identified in Parameter Data To.

5.7.1  Example

The calibration information for a 3T weak-motion velocity sensor might look like the following:


VPC=3.153, 3.147, 3.159

G=1010, 1007, 1002

COILCONST=0.02575, 0.01778, 0.01774






Note: 5TC accelerometers use 1 Ω calibration resistors, and their coil constant is set to 1.

For information on the file, calvals.txt, which stores these values, see section 16.2.

5.7.2 Six-channel digitisers

When working with six-channel digitisers, you have a choice:

Other than the stream names, the effects of both methods are identical so you should decide based on whether having two serial numbers appears natural in your application or not.

You can programme a second serial number:

5.8 Other features

The main menu also provides some miscellaneous facilities:

Choose File → Save Program State to save Scream!'s configuration file immediately. This file is read whenever you start Scream!, and any changes are written back whenever you close it. Under Microsoft Windows, the configuration file appears as scream.ini in the c:\scream directory; under Linux, it is saved in $HOME if this variable is set, otherwise the same directory as the Scream! program file. You can change the name and location of the configuration file with a command line option (see section 16.1).

Choose File → Application Caption… to change the title of Scream!'s Main Window. This is useful if you have several copies of Scream! running on the same computer (e.g. to run multiple network services).

Choose View → Stay On Top to keep Scream!'s Main Window on top of all other Scream! windows at all times. Other applications may still cover Scream!'s Main Window.