USER GUIDE
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Late Entry:
This service provides continuous call in progress updates to allow latecomers to join a
communications channel. This is not a service but an air interface feature the allows a trunked
radio terminal to behave in a s imilar way to conventional PMR terminals. For example, if a
user turns on their TETRA terminal the control channel will automatically divert the user's
terminal to a talk group call, if a call is already in progress. Similarly, if the user's terminal has
been outside radio coverage, for example in tunnel, the control channel will also divert the
user's terminal to a talk group call assuming a call is already in progress.
Ambience Listening:
This service is defined as the facility whereby a control point may place a TETRA MS (or LS)
into a special type of individual voice call tele-service so that the called MS transmits without
any action from, or indication to, the called user. Ambience listening only is set-up if the called
unit is not already engaged in a call.
In the same way, Ambience Listening supplementary service does not prevent the affected
user form making or receiving other calls.
Dynamic Group Number Assignment(DGNA):
This service allows the creation of unique Groups of users handle different communication
needs and may also be used to group participants in an ongo ing call. This service is
considered by many public safety organisations to be extremely users in setting up a common
talk group for incident communications. For example, selected users from the Police, Fire and
Ambulance could be br ought together to manage a major emergency where close co-
ordination between the three emergency service is required. Similarly, DGNA is also
considered useful for managing incidents by other user organisations such as utilities and
transportation.