When a device initiates an emergency call (DN radio or Smartphone), a new ‘dynamic’ group is created.
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)
2. All devices are listening for this ‘Emergency’ group. (unless receive emergency calls is set to disabled)
DN Radios:
Making an emergency call:
To initiate an emergency call, press and hold the top ‘orange’ button for >2s. Emergency calls can also be initiated automatically in Lone Worker or Man Down modes of operation
Receiving an emergency call:
Dispatcher:
Lets assume the dispatcher is the only device set to receive emergency calls.
When an emergency call is initiated from a device, the ‘Emergency’ group/channel is created, and will be transmitting ‘live mic' continuously (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 to talk back to the initiating radio. (if they press PTT without doing this, they 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 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.