E F Johnson Company 2425M70 Benutzerhandbuch

7-22

The problem with this operation is that every time a different talkgroup is selected, the 
access permission may be different and a different site may need to be accessed. This 
could result, in a worst case, in a delay of up to 30 seconds in finding a new site. This 
could occur if there are no valid sites for the new talkgroup in the dynamic site list.

This feature is intended to enhance roaming performance, especially when system level 
steering through radio or talkgroup permissions is used.

To use system channel resources more efficiently, some system operators are using system 
access permissions to steer certain talkgroups to particular sites. For example, a police 
department may be allowed to use only Site 1, and a public works department may be 
allowed to use only Site 2.

A Wide Area Scan can be programmed to minimize the problem just outlined. This feature 
is programmed on the Talkgroup list screen selected on the P25 System screen. When 
Wide Area Scan is selected, talkgroup site preferences are no longer available. However, 
System Site Preference lists can still be used. The Wide Area Scan feature functions as 
follows:

1 Assume TG1 is selected. If it is the first time this talkgroup is selected, normal 

searching for a control channel occurs according to the hunt methods previously 
described.

2 When another talkgroup is selected, the active valid site for TG1 is stored in EEPROM 

memory.

3 The next time TG1 is selected, the following procedure is performed before performing 

the normal hunt methods previously described.

The last valid site ID and its receive and transmit channel numbers are loaded from 
EEPROM memory.

The dynamic site list is checked to see if any newer receive/transmit channel 
information is available for the last site ID.

The best receive/transmit information is used and the radio checks to see if this 
control channel is available.

The result of the preceding operation is that the radio has a reasonable chance of finding a 
valid site, usually on the first try. This greatly reduces access time, even on systems which 
have highly restricted talkgroup based access.

With this option enabled on a talkgroup, as the talkgroup affiliates with a site that site is 
saved if the mobile is changed to a new talkgroup. When the radio moves back to the Wide 
Area Scan talkgroup, it will attempt to affiliate on the saved site before looking for a new 
site.