Press Room - Three Country Pilot - Aachen - Luik (Liége)

TETRA A-Z

A B C D E F G H I K L M N O P Q R S T U V W X Y Z

Air Interface
standard Interface between radio and basestation. (ETS 300 392-2)

Ambience Listening
special call will activate microphone and transmitter of an radio automaticly by not indicating on the radio. It is possible to hear the environmental sound of the radio with this special call.

Automatic Transmission
funktion to activate PTT for a preadjusted time after pressing emergency call button.

Broadcast Call
call to speak to one or several talk-groups. Broadcast Call is a one-way communication.

Callback Request
transmitting of a status-message to give a signal to another participant to call back.

Cell
area supported by a base radio with radio service

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Direct Call
one type of point to point call. The user is selecting one participant out of a list - stored in the radio - and will automaticily connected by pressing PTT. The called participant will not hear a ringtone the connection is online. To answer the called participant has to push PTT.

Direct Mode Operation, DM0 (Simplex)
in areas without coverage all radios are able to communicate by using Direct Mode Operation, DM0.

Dispatcher
Dispatcher is called the operator in the comando control center. Usualy this person has a display with an overview of all talkgroups and is able to communicate with the talkgroups. Emergency calls are also handled by the dispacher.
Second major task are administrative things like patch of talkgroups, exclude of thefted radios or enter of new radios.

Data-transmission
Data-transmission is splitted in

unprotected data-transmission
protected data-transmission
high protected data-transmission

Diversity Reception
use of two or three antennas to receive a singnal in a better way at the base radio station (avoids singnal level reduction based on standing waves).

Dual Watch
is used in Direct Mode Operation, DM0, to listen to a possible conversation in Trunked Mode Operation, TMO. If a TMO conversation is ongoing it is possible to switch the radio to this taklgroup.

Dynamic Group Number Assignment, DGNA
authorisized user are able to create, modify or delete a new dynamic group. Programming of the radios will be done via air interface.

Emergency call
a call with the highest priority. If there is no capacity in the network running connversation will be interrupted to transmit the emergency call.

FDMA
abbreviation for "Frequency Division Multiple Access". Technical base principle of modern mobile radio networks as Matra-Tetrapol. The available frequency range will be splitted in small frequency channels.

Fixed Area
fixed area for a talk group. A call is only transmitted is this area. Radios out of this area will not receive this call.

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Gateway
special TETRA radio will connect a radio in DMO to the TMO Network.

Group Call
point to multipoint connection. One user is pushing PTT and the conversation will be listened by all participants of the selected talk group.

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High-protected Data-transmission
during the data-transmission a lot of error correction bits will be added. The transmission rate is lower than without error correction.

Inactivity Time
the time after communication activity - using a timeslot - until this timeslot is marked as free.
This function is used for group and direct call.

Individual Call
two radio users are able to communicate. Point to point communication.

Inter System Interface
Interface between two TETRA-Networks. (ETS 300 392-3)

IMEI
International Mobile Equipment Identity - sometimes also TMI Tetra Mobile Identity - defines the equipment identity.

ITSI
Individual TETRA Subscriber Identity. individual user number like a phone number. (ETS 300 392-5) see also ISSI

ISSI
International Short Subscriber Identity. consists of a nationality code (3 digits), network code (4 digits) and user code (7..8 digits)
(compareable to IMSI used at GSM)

Late Entry
this function is used for group calls. The Tetra network is periodically sending out information during a running group conversation that allows radios to participate the group conversation not reachable at the beginning of this group conversation.

Mobile
in the meaning of mobile radio. This radio is in mobile moving.

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PEI (Peripheral Equipment Interface)
equipment interface for data application. (ETS 300 392-5)

Pre-Emptive Priority Call
this call will get immediate a transmitting cannel. If there is no capacity in the network running connversation will be interrupted.

Priority
The network is administrating priority levels to organize the call request and the real network capacity. Specially if the network load is high a waiting-queue will be handled by looking for the priority level.
Emergency call is a call on highest priority level and able to interrupt other conversation.

Protected Data-transmission
during the data-transmission error correction bits will be added. The transmission rate is lower than without error correction.

Pseudo Open Channel
call channel is indicated on the radio as a Pseudo Open Channel. The technical allocation to a physical timeslot is only given if real data (talking) are ongoing. If there is no talking - no real data - the physical timeslot is used also for other talkgroups or data.

Push-to-Talk Button / PTT
by pressing PTT a request to call will be signalled to the TETRA System. The System will seach a free channel and allocate to the request. The radio will promt the free channel and give a sound signal to the user.
Pressing PTT is only necessary in Semiduplex- or Direct-Modus. Using telephone mode will provide a full-duplex mode.

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Registration
after switch on a radio this procedure will register the radio in the network with its own number. This will be used to roam with the radio and it is known in which cell the radio is located.

Repeater
Repeater is a special TETRA-radio providing service in a huge area using Direct Mode Operation.

SDS (Short Data Service)
by using Short Data Service you are able to transmit up to 250 ASCII character. SDS is very similar to SMS in GSM-Network

Shifting Area (dynamc group-call area)
definiton of an area of a group. The cells within this area will only call the radios if a responsible radio.

Status Messages
within the network only a number will be transmitted between the radios to indicate a status. You are able to define a meaning of 64.000 differnt status messages. Status messages are e.g. used to indicate the dispatcher that a car has arrived at a focal point.
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TETRA (TErrestrial Trunked RAdio)
european standard for digital trunked radio and confirmed by European Telecommunication Standadisation Institute, ETSI.

Timeslot
by using GSM or TETRA a frequency-channel is able to transmit a number of conversations at the same time. By using a compression method (Voicecodec) indeed participants telegraph by using shifted timeslots.
TETRA is using 4 timeslots on one frequency-channel to transmit up to four conversation or data transmission at the same time. In a Tetra system the 1^st timeslot is used as organization channel also to transmit SDS and status messages.

Trunking Mode Operation, TMO
the common mode by using TETRA-Network is called Trunking Mode Operation. The radio is registered and logged in into the TETRA-Network. The radio is not in Direct Mode Operation, DMO.

unprotected data-transmission
data-transmission without error corrction and parity bit (highest possible data-transmission-rate)

Visiting Member
participant who is allowed - by the responsible dispatcher - to talk within a talkgroup for a while is called visiting member. Is this visiting member leaving the area of the group the certification will be unload automaticly.

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Waiting-queue
are all coversations-channels occupied requesting participants are administrated in a waiting-queue. Free resources will be given to the requesting participant based on the priority.

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