38 System Feature Overview
April 2011 68007024085
• A radio powers on or joins the system after a long fade and the radio initiates an
Emergency Call. In this instance, there is no radio to service the Emergency Call on the
busy Rest Channel.
There are three major methods to process the emergency alarm and the Emergency Call; all are
configurable through the CPS. They are Emergency Alarm Only, Emergency Alarm and Call, and
Emergency Alarm with Voice to Follow.
2.3.4.1 Emergency Alarm Only
When configured for Emergency Alarm Only, the emergency process only consists of the
emergency alarm part. The number of emergency alarm attempts and their admit criteria are
configurable, and can even be set to retry indefinitely. The number of alarm attempts are controlled
by CPS parameters in the Digital Emergency System settings; these parameters include the
number of polite and impolite retries. The alarm is initially sent regardless of channel activity, and
once the configured impolite attempts are exhausted, the polite retries are executed when the
channel is idle. Emergency ends when:
• an acknowledgement is received,
• all retries are exhausted,
• the user manually clears the emergency, or
• the user pushes the PTT.
No voice call is associated with the emergency when operating as Emergency Alarm Only.
Pressing the PTT clears the emergency, and a standard voice call is processed.
2.3.4.2 Emergency Alarm and Call
When configured for Emergency Alarm and Call, the emergency consists of the emergency alarm
process followed by the ability to perform an Emergency Call. The number of emergency alarm
attempts and their admit criteria are configurable, and can even be set to retry indefinitely. The
alarm is initially sent regardless of channel activity, and once the configured impolite retries are
exhausted, the polite retries are executed when the channel is idle.
Emergency alarm stops when:
• an acknowledgement is received, or
• all retries are exhausted.
The radio still remains in an emergency state. Any follow up PTT initiates an Emergency Call, and
the call includes an embedded emergency indication. If the user presses the PTT before the radio
sends an emergency alarm, the radio stops sending the alarm, and starts the Emergency Call.
While in the emergency mode, all subsequent voice transmissions are Emergency Calls. The user
remains in emergency mode until he manually clears emergency. The only way to reinitiate the
emergency alarm process is to reinitiate the emergency.
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