Dead key on P25 question

[BinaryMode]

When someone on a phase I P25 public safety system dead keys on a radio and dispatch is saying your Mic is open, can the dead keyer actually hear dispatch? Does the radio give priority to dispatch?

Thanks.

Edit-

I feel like I've asked this question before but don't recall. It could have been years ago.

 

[buddrousa]

No unless the system is FULL DUPLEX
Most likely untrained Radio User (Dispatcher)

 

[mmckenna]

No, the guy deadkeying the radio won't hear that.

But, the reason dispatchers do it is because if they have both an mobile radio and a portable, like a police officer, the system can be set up so the dispatcher can override the repeat function and the officer may hear them on their other radio, or the radio of someone nearby.

 

[GlobalNorth]

The reason many dispatch centers do this is because they honestly do not comprehend how radio works and think it is like a telephone. They knew how to enter stolen works of art into NCIC, but got no education about how radio works.

My former agency told us to never have a portable radio on while using a mobile radio. The comm supervisor who had started dispatching when Teddy Roosevelt was Commissioner of the NYPD didn't like the feedback squeal and would complain loudly on the radio about it. She thought that the radio airwaves were hers.

 

[KE4ZNR]

No, the guy deadkeying the radio won't hear that.

But, the reason dispatchers do it is because if they have both an mobile radio and a portable, like a police officer, the system can be set up so the dispatcher can override the repeat function and the officer may hear them on their other radio, or the radio of someone nearby.

Yep. To add to this competent system admins set a TOT (Time Out Timer) so that when there is an "open mic" it stops transmitting after a period of time and de-keys. From Motorola's CPS:


On the system I help manage/maintain we usually set our TOT to 60 seconds. Over the years we have found that a minute usually works best for us but other system admins may have different TOT settings.

 

[mmckenna]

On the system I help manage/maintain we usually set our TOT to 60 seconds. Over the years we have found that a minute usually works best for us but other system admins may have different TOT settings.

Yeah, 60 seconds is more than enough, unless we're talking about ham radio operators.

I've run across radios programmed for 3 minutes before. I think that was either what it defaulted to, or someone thought it was really needed.

 

[KevinC]

All the more reason to go TDMA.

 

[ramal121]

TDMA has the ability to interrupt a transmission and dekey a radio. Whether this is used to thwart butt dialers I can't say.

 

[KE4ZNR]

All the more reason to go TDMA.

Don't you rush us
We are happy with our little ol' FDMA setup thank you very much.

 

[ecps92]

When someone on a phase I P25 public safety system dead keys on a radio and dispatch is saying your Mic is open, can the dead keyer actually hear dispatch? Does the radio give priority to dispatch?

Thanks.

Edit-

I feel like I've asked this question before but don't recall. It could have been years ago.

Same answer as Analog - NO

 

[Echo4Thirty]

All the more reason to go TDMA.

Is this implemented in ASTRO25 trunking? I know they did it in DMR, but I have never seen the ability for a P25 SU to be configured for interrupt on Phase II.

I always thought this was needed and could be good for officer/fire safety.

 

[KevinC]

Is this implemented in ASTRO25 trunking? I know they did it in DMR, but I have never seen the ability for a P25 SU to be configured for interrupt on Phase II.

I always thought this was needed and could be good for officer/fire safety.

Absolutely. It's done in PM, not the subscriber.

 

[Echo4Thirty]

So in phase II operation, the radio would just naturally dekey when the OP transmits? I have never seen this functionality. Does the OP have to issue a command for the SU to respond?

 

[KevinC]

So in phase II operation, the radio would just naturally dekey when the OP transmits? I have never seen this functionality. Does the OP have to issue a command for the SU to respond?

It's per RID and any time it keys you can talk over someone else, so you have to careful which RID;s have this ability. The stuck mic subscriber will dekey while the other unit is keyed up but will return to transmitting after the interrupter dekeys. I thinks it's called "allow to interrupt", but I could be mistaken.

I "believe" it was implemented on battalion chief radios after the big hotel fire due to that one firefighter falling on her E-Z Com big red button and kept keying up.

 

[Echo4Thirty]

It's per RID and any time it keys you can talk over someone else, so you have to careful which RID;s have this ability. The stuck mic subscriber will dekey while the other unit is keyed up but will return to transmitting after the interrupter dekeys. I thinks it's called "allow to interrupt", but I could be mistaken.

I "believe" it was implemented on battalion chief radios after the big hotel fire due to that one firefighter falling on her E-Z Com big red button and kept keying up.

Ok that makes sense. I would also assume it could be configured for a console RID? I could see this feature being a double-edged sword if not implemented properly.

I have learned something today and add it to my collective knowlege!

 

[KevinC]

I would also assume it could be configured for a console RID?

Sure. But I would enable it on select consoles only.

 

[BinaryMode]

Very interesting, folks. Thank you!

 

[BinaryMode]

No, the guy deadkeying the radio won't hear that.

But, the reason dispatchers do it is because if they have both an mobile radio and a portable, like a police officer, the system can be set up so the dispatcher can override the repeat function and the officer may hear them on their other radio, or the radio of someone nearby.

Is this via RID? Phase 1 has that capability?

 

[KevinC]

Is this via RID? Phase 1 has that capability?

As long as the console is wireline it works on Phase 1 or conventional or almost any flavor of repeaterized communications.

 

[MTS2000des]

It's known as console priority, and is standard in all wireline control. The dispatch/console operator hears the SU audio but can always override the outbound audio on their selected resource. Allows them to "control the air" while still allowing SU's to key up but only the console will hear them and the SU audio isn't repeated back out while the console is keyed via instant transmit.