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By default,
1. Emergency calls are semi-full duplex. The initiating radio transmits ‘open’ mic continuously (no TX/RX cycles) on the ‘Emergency’ group. (not on the current selected group). The receiving radio or dispatcher must press PTT to talk back to the initiating radio (or smartphone) and while PTT is pressed, the call is then in ‘full duplex’ mode. (i.e. transmitting and receiving simultaneously).
2. All devices are listening for this ‘Emergency’ group. (unless receive emergency calls is set to disabled)
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Receiving an emergency call:
When a DN radios receives receive an emergency call, there is an audio alert, and the LED flashes Red. In addition, the radio will hear the live mic ‘live’ microphone voice audio from the initiating radio.
There is an option now to accept or reject the emergency call, by using the ‘right’ or ‘left’ keys below the display.
Reject:
Accept: Dispatcher:
Lets assume the dispatcher is the only device set to receive emergency calls.
(RH key) the audio alert is cancelled, and the radio joins the emergency group.
Reject: (LH key) the radio exits emergency receive mode and resumes normal operation on the selected channel.
Dispatcher:
When an emergency call is initiated from a deviceDN radio (or smartphone), the ‘Emergency’ group/channel is created, and will be transmitting ‘live mic' voice is continuously transmitted (no cycles). The dispatcher will see this new group (RED highlight) added to the list of existing channels. It will also hear the audio from the live mic. (there are options in how the dispatcher views/hears/responds to emergency calls in the T.commander config)
At this point there are options in how to set up the dispatcher config to respond to emergency calls.
The 'default’ set up requires the dispatcher to manually join the Emergency group (by clicking on it) if they want and then to press the PTT button to talk back to the initiating radio. (if they press PTT is pressed without doing this, they the dispatcher will just transmit on the currently selected channel). The Emergency calls are semi-full duplex, in that the dispatcher needs to press PTT to talk back, but while pressing PTT, it is full duplex.
The call will continue until either the initiating radio cancels the emergency, or it is cancelled from the dispatcher. (right click on channel name).
Note, when an emergency call is cancelled, the DN radio will revert back to the current previously selected channel, and the emergency dynamic group is only cleared when the last user leaves the channel. (in some instances the dispatcher may be the only user left on the channel, in which case they must then manually switch channels or cancel the emergency)
One useful setting for the dispatcher is to use 'enable talkgroup scan for emergency channels) which will automatically move to the emergency group.