Motorola MTP850 Ex Product Information Manual page 62

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6 Direct Mode Operation (DMO)
TETRA DMO enables the terminal to directly communicate with another TETRA terminal or group of
terminals directly, without the need of an intervening base station.
The terminal supports Direct Mode Operation service identity as described in the Air Interface
standard [Ref 8].
6.1 DMO Mode
To communicate directly with another terminal not through a SwMI, the user enters into a special
mode that allows Direct Mode (DMO) communication. To return to normal operation, the user
switches back to Trunking (TMO) mode.
In DMO mode, the user is prevented from changing modes to private, PABX or Phone modes. All
menu items are available, although some functions from the menu are restricted (sending status
messages for instance).
In DMO mode, the RSSI level is displayed to the user only when the terminal is receiving.
6.2 DMO Group Call
The user can initiate a DMO group call and participate as a listener of a DMO group call.
The user can select one of up to 1024 groups, each of which has an associated DMO frequency.
There will be a mapping between DMO and TMO talkgroups, such that when moving from TMO to
DMO or vice-versa the appropriate group will be selected. Calls initiated by the terminal will be to the
selected group. Only incoming calls to the selected group and the open group (See Paragraph 6.5
"DMO Inter-MNI Calls") on the selected frequency will be joined by the terminal; TG scanning is not
supported.
The terminal supports call initiation and acceptance of call changeover, enabling the talker ("DMO
master") to change within a DMO group call.
If Talking Party ID (TPNI) is received in an incoming group call transaction (or received in DM-INFO)
it will be displayed to the user. It will also be sent by the terminal in outgoing group transactions.
The terminal will send late entry signals ("occupation messages") periodically while transmitting in a
DMO group call. The terminal will detect late entry signals sent out by other DMO terminals.
6.3 DMO Private Call
Private Call in DMO (a.n.a. Direct Mode Individual Call) allows the user to dial a selected TETRA
terminal rather than currently selected talkgroup. Only terminal to terminal communication is
supported. Repeater and Gateway are not supported. When a DMO Private Call takes place,
terminals not involved in this call receive the channel busy indication.
Current implementation does not support the presence check. This implies that the calling party
does not know if the called party is available when the call is originating.
The Terminals are identified by Short Subscriber Identities. DMO Private Call is a half-duplex call.
6.4 DMO Emergency
The terminal supports initiation and acceptance of DMO Emergency group calls, this includes
support of call pre-emption. Emergency calls via gateway will also be supported. If Emergency Call
6866588D21-D Chapter 2 - MTP850 Ex/MTP810 Ex Product Information Manual
Services and Feature Description
March 2009