Wow. I'm confused now.
I may have to start a thread just for "ruthless pre-emption."
I'm reading some actual Motorola documents about ruthless pre-emption and from what I gather, the purpose is focused on granting a voice channel to an emergency call when the system is busy by cancelling a low-priority call. It does address the issue of RF contention (the user transmitting on the old "cancelled" call will not receive the system's command to go idle, and that user transmitting on the input frequency may interfere with the emergency user transmitting on the same frequency).
What slicerwizard is saying is that his local Smartnet is set up where ruthless pre-emption is more focused on an emergency activation that occurs while the emergency user's talkgroup is in use, and the process of moving the emergency user, along with all other monitoring users to another available voice channel, leaving the user transmitting the call on the talk group basically talking to nobody.
Any other input as to which one is correct (as I suspect only one is the actual correct answer)?
I have to go back in time with my memory. . . .
When my agency installed a Smartnet Type II System in 1995-1996 and training was conducted prior to live cutover to users being on the system, we had the opportunity to test a lot of things out.
One of those was ruthless pre-emption.
Things to keep in mind (For my example I am using a 5 channel trunking system)--This example was tested and verified. . . - - -
CH 1 in use by Control channel
CH 2-5 in use for voice calls
4 talk paths are available on a 5 channel TRS
If all 4 talk paths are in use there are 4 radios that are actively transmitting on the repeater inputs and --NOT-- monitoring the Control Channel or receiving in any way shape or form.
User hits emergency button on radio. Ruthless preemption is enabled on system and Hot Mic is enabled on radio.
Emergency Alert hit consoles but in regards to Hot Mic Nothing happens. . . Until one of the talk paths clears
Reason nothing happens is there is no available talk path on the system.
There is no way for the central controller to tell a radio to stop transmitting since the radio is not actively receiving. Due to nature of FM and strongest signal wins, turning the radio on that has declared the emergency would not positively give the radio access to the dispatcher on voice if there is no talk path available.
However, the radio is now at the top of the queue for a channel grant when it becomes available.
Further in regards to Hot Mic on Emergency. . .
If the radios are programmed and trunking controller set up for Message Trunking this method works.
If the radios and trunking controller are setup for Transmission Trunking the radio will not key up with Voice traffic if there is traffic active on the talkgroup that the emergency is declared on.
This is going back almost 15 years but definately remember what we did in testing.
Tony