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Tetra Apps

In this part TETRA apps all available systems and devices are summarized, which assure special functionalities based on the TETRA infrastructure. These are for providing value added features inside the TETRA system (e.g. centralized communications recording), or outside the system (e.g. vehicle tracking) new functionalities for the system users.

Individual Communications Recording

Individual communications recording might be useful when no centralized system is applied. Individual recording is foreseen only for dispatcher workstation applications.

CRU-2AN can advantageously used for DWS workstations when analogue voice recording is enough.

CRU1V is a flexible unit applicable for fix and vehicle mounted workstations.

General Introduction

The CRU-2AN is a small sized, IP based, two-channel voice recording system with two symmetrical analogue line inputs and two microphone inputs. CRU-2AN is designed for recording the voice communication of TETRA DWS, but it also can be used as a general voice recorder in wide area. With an optional cable, which can be connected to TMR880 desktop radio handset’s front connector it also can record the TMR880’s voice communication (if recording of call related information and SDS messages is required see our CRU-1 product in the TETRA APPS). Using the CRU2-AN’s microphone inputs beside the DWS voice recording the voice surveillance of the dispatcher's room is also possible.

The device works at very low power consumption (<1W) and can record of the voice communication of two DWSs simultaneously because the CRU2-AN has two separated logical voice recorders. As a special feature the equipment can be configured as a stereo voice recorder and can record the two directions of a call into a stereo file as left/right channels.

The functional block diagram of the CRU-2AN is shown below.

functional block diagram

The CRU-2AN can be configured and set up by its client application (CRU-2AN-PC software). This client application can run under WINDOWS 2000/XP/VISTA on any Pentium 4 (or on of >1GHz Pentium 3) configuration. No special requirements are needed.

Operation Details

There are two available basic types of recording. On one hand, the CRU-2AN can record using its SD cards independently. The applied file system is FAT32, so removing the SD cards and inserting them into a card reader the records can easily be carried for a PC and can be copied and listened under WINDOWS. The device automatically selects the available card so it is possible to remove a full SD card while the other one is active. On the other direct recording on the PC’s HDD is also possible with the client application. Furthermore parallel recording on the CRU-2AN’s SD card and on the client PC’s HDD can also be set up. With the client application the inputs can be listened in real-time (independently from the recording). The recorded files can be played back with the client application. Two types of playback are possible: local or remote. Local playback can be used to play the records stored on the PC’s HDD or stored on the inserted SD card. Remote playback is used when the SD card is not removed from the CRU-2AN. In this case the files can be played through the IP connection. The playback does not disturb the existing recording (simultaneous recording and playback on the SD card). In the client application the current status of the SD cards are shown: active recordings, number of records, available free space, SD card operation status, etc. The recording can be continuous or VOX triggered. A high efficient adaptive voice detector is implemented for both channels. On the SD card circle recording can be set up. In this case the device handles the two SD card like one storage, and in case of full SD cards the oldest files are deleted automatically.

Audio File Format, Protection

The audio data is stored in a vendor specific encrypted and electronically signed format. The files can be carried and copied under windows with the file manager because the files are standard FAT32 files. The content is specific and is protected with electronic sign. The playback is possible with the client application. The client application verifies the electronic sign and decodes the applied encryption. From the client application all the files can be exported into standard „wave” files and after this, files can be played with a standard media player.

On demand, the format on the SD card can be changed into standard WAVE format. In this case the records on a removed SD cards can be listened without any client program activity. No additional client program is required (only for set up). The configuration is stored in the CRU’s flash memory).

The exact time stamps of the start and the end date/time of a speech communication (VOX trigger begin/end) are attached inseparably to the speech content.

Other Technical Parameters

  • Two microphone input with 0-50dB adjustable gain and +30dB selectable with jumper
  • Two symmetrical (balanced) line inputs towards DWS recording output or other audio sources. Maximum acceptable level is +6dBm. 0-50dB adjustable gain can be applied
  • Independent automatic gain controls for both channels
  • Two independent voice activity detectors
  • Selectable sampling frequency (8KHz, 16KHz, 24KHz) , 8KHz is recommended for DWS recording
  • 1x stereo or 2x mono operation modes
  • Low power consumption (<1W)
  • 10/100Mbps ethernet connection
  • Applicable SD cards: 1GB, 2GB SD, 4GB, 8GB, 16GB SDHC or UltraII cards
  • Interoperation with Hungarocom’s centralized archive recording system (optional)
  • High storage capacity: with two 16GB micro SDHC card and with 8KHz sampling frequency the capacity is about 45 day continuous speech

The picture of the device is shown on the next Figure.

A typical menu of the client application is shown on the figure below.

client application
This device is the communications recorder of TMR 880 and TMR 880i dispatcher workstations for fix and vehicle mounted applications.


The main caharacteristics of the device are the following:

  • recording of voice communications
  • start/stop of the recording by means of line signals, or VOX detector
  • recording of SDS and Status messages
  • simultaneous recording and playback is possible
  • the communication information is stored on an encrypted way
  • voice and call related data are stored in the same file with an inseparable way
  • the recorded data is guarded against manipulation and sabotage by „electronic signature”
  • filtering of information according to the customer’s need
  • export possibility of the recorded information in standard WAV file
  • remote access via LAN or WAN
  • remote operation and management of the devices
  • connection possibility to centralised data base servers and centralised storage
  • connection possibility of external VGA monitor
  • length: 300 mm, width: 165 mm, height: 50 mm
  • power supply: 12V DC/220VAC with 12 V power supply unit

Centralized Communications Recording

The application of Airbus DS’s TETRA Release 5 and above provide new possibilities in the field of communication recording as well. Hungarocom’s CMST-C system is developed for the handling of the new features of Release 5. beside the usage of its economical, network level, flexible, high power communication recording archiving and processing capabilities.

Communication (archive) recording means recording of all call related data information together with the speech or data communication. The traffic cases included in the communication recordings are the following:
  • event monitoring of group communication (without audio)
  • group data communication (status and SDS messages)
  • group calls (audio)
  • data (status and SDS messages) communication of mobile and dispatcher terminals (without audio)
  • group and individual calls of mobile and dispatcher terminals (audio)
  • it is also possible to monitor the communication in real-time with its simultaneous recording
Archive Recording

Vehicle Location

Object Tracking

TETRA system can be used for highly reliable data transfer for application of automatic object tracking (OT) of TETRA users. The data transfer can be provided by:

  • highly reliable SDS-TL data transfer method via the TETRA system. These messages are transferred via controlling channels and do not need the occupation of speech channels. This means that practically the speech traffic does not influence the transfer of the SDS-TL messages used for OT purposes.
  • data messages via the data part of the TETRA system.

The figure below shows the principle of the system:

TETRA vehicle sets (e.g. TDR 880), or modern handsets containing GPS receiver as well send the vehicle location by means of SDS-TL, or data messages towards the central units of TETRA.

Integrated GPS improves efficiency. An integrated GPS receiver enables positioning of the radio users based on their geographical co-ordinates. The radio’s position can be transmitted over the TETRA network upon request either automatically at certain time or distance intervals, or as a reply to a single request. Using a separate positioning application, the unit’s position can be shown on a digital map, allowing command and control to trace and contact field staff based on their geographical location.

At the other end Hungarocom’s CMS-OT central system receives the SDS-TL, or data messages via TETRA’s TCS connectivity server/GGSN gateway and transfer them towards the mapping and processing subsystems.

Data Collection And Voice Announcement

TETRA system can be used for highly reliable data transfer for applications like measurement data collection and centralised selective voice announcements for areas.

Typical application of the system is collecting meteorological or environment pollution surveillance data from rarely distributed measuring (meteorological) stations.

The data transfer is provided with highly reliable SDS-TL data transfer method via the TETRA system. These messages are transferred via controlling channels and do not need the occupation of speech channels. This provides a simple reliable and economical data transfer method for the secondary use of an existing TETRA network.

This task can be combined with selective voice information sending for a selected area by means of signal or speech announcements. Typical application is information communication in case of disasters but this method can also be used for transmitting voice information or coverage for pre-selected communities using high power outdoor loudspeakers.

TETRA based data collection and voice announcement
Data arriving from the data collector units by means of SDS-TL messages are received by TCS (TETRA Connectivity Server) belonging to the TETRA system and transferred to the TDCS device of the auxiliary system. Data can also be transferred to other servers for further information processing.

For generating voice announcements the voice information from the workstations of the relevant information processing networks are transferred via E1 or LAN connections alternatively for the TETRA system. Via the TETRA system group communication pathes are established which serve for announcement of a defined combination of areas and outdoor announcers.

Lawful Interception

CMS-T together with the mediation device serves for TETRA system level lawful interception both for voice and data communications.

CMS-T is an universal robust system for nationwide networks applications however a simplified versatile economic version was also developed which fits better to the requirements of smaller target networks. This is a special application for the very complex function of the TETRA system. CMS is able to intercept all kind of features provided by the TETRA system:

  • individual calls
  • group calls
  • SDS, Status messages
  • packet data
  • tracking data
  • subscriber related events

CMS-T is composed from two basic part: the mediation device connected to the central point of the TETRA system, and the information storage and managing centralized system located in the remote end. The main characteristics of the operation:

  • Storage of intercepted information for the authorized time.
  • Composition of target structure.
  • Playback of communication content with the relevant call related information (CRI).
  • Real-time surveillance. The real-time playback is a no wait process.
  • Report writing. The function is supported by an integrated word processor software.
  • Copies of intercepted information. Upon request designated sessions of the recorded information are copied on different storage media for offline use. Such media include CD, DVD etc.
  • Long-term archive. Sessions or the full contents of communication of designated information sources are stored in the long-term archive for later use and for authentic evidence purposes.