E F Johnson Company 2425795 사용자 설명서

Viking™ VP600 Portable Radio Operating Manual

6-15

When a call needs to be passed to a radio at another site, the traffic from one site to 
another is sent out over the control channel to the radios. When a radio is scanning, it is 
monitoring the call information being sent out over the control channel. The radio 
compares the call information (talkgroup and voice channel handling the talkgroup) to the 
scan list to see if any of the talkgroups it is scanning are receiving a call. If it finds a 
match, the radio moves to the voice channel for this call. If no one is registered on a 
talkgroup on the site being scanned, the call information for the call is not sent out by the 
Control Channel (because the Zone or Site Controller did not see a requirement to pass the 
information for this call) and the call will not be received.

For example: Radio 1 is on a call on talkgroup 1 on Site 1, Radio 2 is on talkgroup 2 on 
Site 2 and scanning. The call on talkgroup 1 from radio 1 is not heard by radio 2. Then, if 
radio 3 registers on talkgroup 1 on site 2, the call from radio 1 on site 1 will go to site 2. 
Radio 2, radio 3, and any other radios on site 2 and scanning, will hear the call.

The Viking VP600 Portable radio supports Dual Priority talkgroups in all trunking and 
conventional formats. 

One talkgroup in the scan list can be designated a priority talkgroup by programming or it 
can be the selected talkgroup. When scanning, messages on a non-priority talkgroup are 
interrupted by messages on the priority talkgroup. Priority scanning must also be 
supported at the system level for it to occur as programmed in the radio. P25 trunking 
supports dual priority scan, therefore two priority talkgroups can be selected.

The Control Channel handles all traffic for the radios and communicates which talkgroups 
are using which channels. If the radio “receives” the ID for one of its talkgroups, it can go 
to that channel and hear the talkgroup. When the radio is on the voice channel, it cannot 
receive information about which talkgroups are on which channel. The radio will not 
know about any new talkgroup activity until it finishes the voice channel and returns to the 
Control Channel. 

If a talkgroup is set as a Priority Monitor talkgroup on the system, the system sends the 
talkgroup’s call information over a voice channel so it can be detected and move to this 
priority call. So even if the radio cannot hear the Control Channel, it will receive the call 
information and switch to the channel with the priority call.