PoC: Emergency Calls (How it works)
- Mike Hirst
The aim of this article is to give an overview on the basic implementation of Emergency mode for PoC devices.
When a device initiates an emergency call (DN radio or Smartphone), a new ‘dynamic’ group is created.
(a dynamic group is a temporary group)
DN radios participating in the emergency call move to the emergency dynamic group.
note: Dispatchers have server and user settings to configure the action taken when receiving emergency calls - e.g. talkgroup scan for emergency channels.
Emergency calls are received server wide by default. i.e. radios will receive emergency calls initiated from users in any other channels (Talkgroups) on the server, regardless of which channel or ‘Team’ they are currently a member of - or alternatively,
each user account allows restricting incoming emergency calls to be limited to only those initiated from another user in the same channel (enable ‘ignore emergency calls from other channels’). note: This is an ‘either/or’ setting and when enabled for a user, emergency calls initiated from users in other channels will not be received)
These settings are found in T.Commander under the ‘emergency’ tab per user account.
By default, (options available)
1. Emergency calls are semi-full duplex. The initiating radio transmits ‘open’ mic continuously (no TX/RX cycles) on a new ‘dynamic’ Emergency group. (not related to the current selected group). The receiving radio or dispatcher must press their 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 always listening for this ‘Emergency’ group when ‘receive emergency calls’ is enabled.
note: 'receive emergency calls' is enabled/disabled per user via T.Commander. DN radios additionally have a menu option for disabling emergency RX/TX which allows user control. (but cannot override server user settings if emergency is 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:
When DN radios receive an emergency call, there is an audio alert, and the LED flashes Red. In addition, the radio will hear the ‘live’ microphone voice audio from the initiating radio.
There is an option to accept or reject the emergency call, by using the ‘right’ or ‘left’ keys below the display.
Accept: (RH key) the audio alert is cancelled, and the radio joins the emergency group. Press PTT to talk back to the radio sending the emergency call.
Reject: (LH key) the radio exits emergency receive mode and resumes normal operation on the selected channel.
Cancelling an emergency call:
Press the RH key below the display (during an emergency call) to exit emergency mode. (or long press the top orange button for less than 2 seconds)
Dispatcher:
When an emergency call is initiated from a DN radio (or smartphone), the ‘Emergency’ group/channel is created, and ‘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) and then to press the PTT button to talk back to the initiating radio. (if PTT is pressed without doing this, the dispatcher will transmit on the currently selected channel).
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 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 the dispatcher to the emergency group.
There are also options (set in T.Commander) to acknowledge emergencies (this disables every other functionality until acknowledged) and to add a pop up on an incoming emergency - it is advisable to look over and test the other settings available here, e.g. time out timer for live mic, to suit the customer requirements.
