Running out of Freq for a Trunked System

[dimab]

What happens to transmissions when all available comm. frequencies in a system are used up at the same time. Does a user receive an error when trying to TX or is it queued via recording?

 

[seamusg]

What happens to transmissions when all available comm. frequencies in a system are used up at the same time. Does a user receive an error when trying to TX or is it queued via recording?

[FONT=&quot]Depends on the radio system. The radios on the Warren, MI system will buzz on a busy, unless it's PD of FD. In their case lower priority traffic will be disconnected and the channel grant request will be queued for the non PD and FD traffic. The feature is called ruthless preempt. The Warren system is setup to give PD and FD first choice.[/FONT]

 

[scannerfreak]

If you do get the busy "bonk" sound, Some radios will also alert you when a channel becomes available.

 

[bwhite]

A poster that is apparently very thorough knowledge of this answered this question about 6-8 months ago including stats as-to how many transmissions didn't go thru because of this. Very interesting. Unfortunately I can't recall enough of the message to string-search for it; I believe it was in the Trunking Forum.

 

[dimab]

good enough for me. I pretty much imagined it working that way, with priorites and such, but wanted to confirm it.

bwhite, I'd love to read the finer details of how this priority stuff works. i'll search around.

 

[N_Jay]

[FONT=&quot]Depends on the radio system. The radios on the Warren, MI system will buzz on a busy, unless it's PD of FD. In their case lower priority traffic will be disconnected and the channel grant request will be queued for the non PD and FD traffic. The feature is called ruthless preempt. The Warren system is setup to give PD and FD first choice.[/FONT]

I think Ruthless preemption is only used for emergency transmissions (emergency button pressed)
All other priorities go to queue (usually very short)

There is no recording.

 

[UPMan]

Busy Message

 

[N_Jay]

Busy Message

Very funny.

Most people just call it a BONK.

 

[seamusg]

I think Ruthless preemption is only used for emergency transmissions (emergency button pressed)
All other priorities go to queue (usually very short)

There is no recording.

From what I understand from a Radio Tech for Macomb Co. All alarms including emergency button are on the control channel, he also said the Ruthless Prempt has never been used on the Warren system even on the old system, but is there if they need it. He did say there is a priority system set up with the Radio ID's. 120XXXXX is dispatch, 101XXXXX is Warren PD, 102XXXXX is Warren FD and 103XXXXX is Centerline PD.

 

[bwhite]

I think this is the prior thread I referred to below:
http://www.radioreference.com/forums/showthread.php?t=25226&highlight=busy

 

[N_Jay]

From what I understand from a Radio Tech for Macomb Co. All alarms including emergency button are on the control channel, he also said the Ruthless Prempt has never been used on the Warren system even on the old system, but is there if they need it. He did say there is a priority system set up with the Radio ID's. 120XXXXX is dispatch, 101XXXXX is Warren PD, 102XXXXX is Warren FD and 103XXXXX is Centerline PD.

Yes, the emergency notification is sent in on the control channel (just like all other channel requests).

Ruthless preemption refers to the granting of a voice channel, and (to my knowledge) as system can NOT be set to do that except with an emergency button press.

Most agencies do not use ruthless preemption due to the user confusion it causes.

 

[slicerwizard]

Emergency Ruthless Preemption:

If all voice channels are occupied when an emergency call is made, then the unit initiating the emergency will be allowed access to the voice channel with the lowest priority user currently assigned. It must be noted that until the current user de-keys, there will be RF contention between the emergency user and the currently transmitting unit. Once the non-emergency user de-keys, the channel belongs to the emergency user.

 

[SCPD]

There is another from of preemption that can be initiated by a dispatcher at a console. Unlike "ruthless preemption" where two radios transmit on top of each other on the repeater input, the console is wired directly into system so that the dispatcher's voice can supercede the repeater's own input.

Pressing the "E" button to get the dispatcher's attention is actually more effective. You might not be able to TX until the current talker unkeys - but you'll always be able to hear the dispatcher answer back (who in turn can worst-case do an I-call direct to the radio on a separate channel).

-rick

 

[Al42]

but you'll always be able to hear the dispatcher answer back (who in turn can worst-case do an I-call direct to the radio on a separate channel).

If all channels are in use?

 

[RocketNJ]

Most systems I've worked on have a priority structuring with public safety groups having higher priority than road department and other users.

Most systems are configured for top of queue where the user gets a busy signal and will be assigned next available channel.

Ruthless preemption will drop the call in progress and give the dispatcher of the user with the emergency or priority call the channel. The problem is the other user's radio is still transmitting and doesn't hear the data to stop transmitting. Now you have two users transmitting on the same freq at the same time. This could cause the user's emergency transmission to not be heard at all.

So again, due to the chance a call might not be heard, most systems are not set for ruthless preemption.

 

[grem467]

If all channels are in use?

if all system channels are in use, then there would be no available channel to place an Icall.

 

[SCPD]

If all channels are in use?

This is sticky (but a good question).
If all channels are in use AND the person to whom the dispatcher wants to address is on an ACTIVE talkgroup - the dispatcher can preempt the audio of the active talkgroup. Everyone on that talkgroup will hear the dispatchers's voice instead of the long-winded mobile that happened to be talking at the time. The long-winded yakker won't know they've been preempted.

-rick

 

[greenthumb]

...but I think his question was regarding the private call from the console. If all channels are busy, the console still won't be able to place a private call to the radio with the emergency until there is an available channel - which the console won't get a grant before the radio with the emergency since the radio with emergency will be at the top of the queue (priority 1).

Also, regarding ruthless pre-emption - this is a pre-programmed feature by system, so either the system uses ruthless pre-emption or top-of-queue for emergency calls. Not all systems are set up for ruthless pre-emption.

 

[seamusg]

...but I think his question was regarding the private call from the console. If all channels are busy, the console still won't be able to place a private call to the radio with the emergency until there is an available channel - which the console won't get a grant before the radio with the emergency since the radio with emergency will be at the top of the queue (priority 1).

Also, regarding ruthless pre-emption - this is a pre-programmed feature by system, so either the system uses ruthless pre-emption or top-of-queue for emergency calls. Not all systems are set up for ruthless pre-emption.

My undestanding is that dispatch console gets the ruthless pre empt, since they get the alarm, so they will override.

 

[morganAL]

If Bob the Cop is babbling on the dispatch TG about Mrs Suzie's goats getting out for the 10th time this week and the dispatcher needs to dispatch a bank robbery, all the dispatcher has to do is key up on that group on the radio console and immediately all of the other PD units hear the Dispatcher give out the bank robbery. Bob the Cop's audio is replaced by the dispatcher's audio. The system works this way whether one channel or all channels on the system are busy. Bob the Cop is clueless as he is probably still yakking away.

And yes, these things really happen.

If the dispatcher or any other unit try to transmit and there are no channels available and the TG they want to use is not in use, then the dispatcher gets an audio indication and a message on the console or the radio user gets a high-pitched beep which will be followed by a channel-grant beep in .5 seconds or longer.

This is with an EDACS system using the C3 Maestro consoles. YMMV on other branded systems and/or consoles.