MM-012099-001, Rev. B
8.20.2Priority System Scan
The radio can also be pre-programmed for Priority System Scan. The priority system is the desired or preferred system. While receiving the control channel of the selected system, the radio will periodically leave the selected system and search for the control channel of the priority system. This is done at a pre- programmed rate defined by the value in the Priority Scan Time control, unless the ProScan™ algorithm is enabled, as explained in the following sections. This priority scan timer is reset each time the PTT button is pressed or when the call is received. If the priority system control channel is found, or meets the predefined criteria (ProScan), the radio will automatically switch to the priority system.
8.20.2.1 Enabling the Wide Area System Scan Function
If the radio cannot find the control channel of the selected system and begins to wide area system scan, the radio will only scan for the priority system control channel if the priority system is in the wide area scan list.
8.20.2.2 When ProScan is Enabled
The radio monitors the priority system and will switch to the priority system if the pre-preogrammed criteria ProScan options are met. If ProScan is enabled, the rate at which the radio will scan for the priority system is defined by the System Sample Time control, set in RPM, (refer to RPM On-Line Help). See Section 8.20.3 for more information on ProScan.
8.20.3ProScan
The radio may be programmed for ProScan system scan operation for multi-site applications. ProScan is a multi-site system scanning algorithm. ProScan provides the radio with the ability to select a new system for the radio to communicate on, when the selected system drops below a predefined level. This algorithm enables each radio to analyze the signal quality of its current control channel and compare it with the signal quality of the control channel for each site in its adjacent scan list. The signal quality metric used for the ProScan algorithm is based on a combination of both Received Signal Strength Indicator (RSSI) and Control Channel Verification (CCV) measurements. When the selected system degrades to a pre-programmed level, the radio will begin to look for a better control channel. Once a control channel that exceeds the pre-programmed parameters is found, the radio will change to the new system and emit a tone (if enabled through programming). If the control channel is completely lost, the radio will enter Wide Area System scanning and search the programmed adjacent systems until a suitable control channel is found.
8.21EMERGENCY OPERATION
The radio's ability to declare an emergency, clear an emergency, remain locked on an emergency system and group, and the emergency audio and display freeze can each be enabled or disabled through programming. When an emergency is declared scanning will stop and restarts only after the emergency has been cleared.
8.21.1Receiving an Emergency Call
When receiving an Emergency Call on the selected group and system, an alert beep is heard and 
is displayed. The message *RXEMER* flashes in the display on line two until the emergency condition is cleared.
