System Feature Overview 35
68007024085 April 2011
The emergency alarm is sent first, and depending on configuration is commonly followed up by an
Emergency Call.
An emergency alarm is not a data service, but rather a confirmed command and control signaling
that is sent to a group. More than one radio can be configured on the system to monitor that group,
and be designated to acknowledge emergency alarms for that group. These radios are considered
acknowledging supervisors. There is no user level acknowledgement. The supervisor radio
automatically acknowledges the emergency, and provides an alert to the supervisor radio user.
There are other radios that are designated to only monitor emergency alarms, but are not
permitted to acknowledge them; these users are commonly referred to as non-acknowledging
supervisors. Thus, sending the emergency alarm to a group allows for multiple supervisors to
receive the emergency alarm indication. It is important that only one acknowledging supervisor
should be configured per group and slot; otherwise there may be contention between the
acknowledgements.
The supervisors retain a list of received emergency alarms so that they can keep track of multiple
emergencies. Once cleared, the emergency alarm is removed from the list, and the next one is
displayed. These emergencies are displayed in a last-in-first-out sequence. The supervisor has
the ability to hide the emergency alarm list, so he can contact service personnel to attend to the
received emergency situation. The channel where the emergency alarm was received is displayed
to aid the supervisor when changing channels.
If the user follows up the Emergency Alarm with a voice call while in the emergency mode, his
transmission contains an embedded emergency indication. Any radio user can be configured to
display this embedded emergency indication. Emergency Calls are always processed with an
admit criteria of Always. This allows the Emergency Call to transmit regardless of the current
channel activity. If there is another radio currently transmitting, contention may occur.
The initiating radio supports a feature that is tied to silent emergency and the Emergency Call. The
“Unmute Option” prevents the radio from receiving voice traffic after initiation of a Silent
Emergency. In situations where an indication of an emergency state is not desirable, it is important
to be able to mute incoming voice, that may give away the initiators emergency state. Once the
user breaks radio silence by pressing the PTT and speaking, the radio returns to its normal
unmute rules.
Silent emergency and the unmute options have no effect on data. It is the responsibility of the end
user to make sure data is not sent to a terminal that would divulge any emergency state.
Transmission of data does not clear Silent Emergency.
The channel and group on which a user transmits his emergency is crucial to properly contacting a
supervisor. MOTOTRBO offers the ability for a user to transmit the emergency on a selected
channel or to automatically change to a predetermined channel to transmit his emergency.
Transmitting an emergency on a selected channel (referred to as a “tactical” emergency) is often
useful on small systems where there are only a few groups of users. Each group has its own
specified user that handles emergencies.
Automatically changing to a predetermined channel, referred to as “reverting”, is often useful in
systems that have a dispatch style emergency strategy. Users in various groups and channels are
configured to revert to a specific channel and group to process an emergency. This allows one
user to monitor an “Emergency” group, and all other users revert to him in case of an emergency.
This minimizes the possibility of supervisors missing emergencies on one channel, while
monitoring other channels. After the emergency is cleared, all users revert back to the selected
channel they were on before the emergency. In MOTOTRBO systems, the Emergency Revert
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