Trunking Announcement Talkgroups (ATG)

JoeyC

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This is not necessarily a San Diego question, but more of a P25 trunking question but I put it here because I am more interested in knowing if the current San Diego 700 system and/or the RCS NextGen system uses specific "Announcement talkgroups" and what are their purpose?

Perusing through the Unication PPS software I noticed the option when using Trunking TG-Scan receiving mode to set an Announcement Group (ATG) ID.
The taiwanenglish description given in the software is confusing to me probably because I am oblivious as to what this is, and more importantly if they are utilized on either of the P25 systems in San Diego county.

Can anyone explain? Thanks!
 

mmckenna

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"Announcement talkgroups" and what are their purpose?
I don't know how it differs on a P25 trunked system, but I've had them on my old SmartNet system and my current NexEdge system.

They were talkgroups you could switch to that would basically spam a larger group of users on multiple talk groups I could define. Since my system is used for a lot of other groups, I had an announcement talkgroup set up for each of them. It is/was often used as a way of making an 'all call' to a larger group.

Different than a 'system wide' talkgroup that would go to every radio that was currently registered on the system. I only gave the dispatch console access to that one.
 

inigo88

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This is not necessarily a San Diego question, but more of a P25 trunking question but I put it here because I am more interested in knowing if the current San Diego 700 system and/or the RCS NextGen system uses specific "Announcement talkgroups" and what are their purpose?

Perusing through the Unication PPS software I noticed the option when using Trunking TG-Scan receiving mode to set an Announcement Group (ATG) ID.
The taiwanenglish description given in the software is confusing to me probably because I am oblivious as to what this is, and more importantly if they are utilized on either of the P25 systems in San Diego county.

Can anyone explain? Thanks!
Isn’t set up the city system or RCS to my knowledge, Don could speak to RCS for sure. “All Calls” are only ever made by dispatchers (for example SDPD may broadcast “citywide”), and they are just multi-selects of multiple dispatch channels made on the dispatcher’s console.
 

JoeyC

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Thanks inigo88 I haven't noticed its use either. I haven't paid attention on the new 700 system, but when SDPD multi-selects for a citywide broadcast the 800 system utilizes a separate frequency for each talkgroup patched. I doubt this is the efficient way (as far as radio channel usage is concerned) to accomplish this, (although it may be the easiest way on the console), but since it only occurs for very short periods of time, it probably usually isn't a problem.
 

inigo88

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Thanks inigo88 I haven't noticed its use either. I haven't paid attention on the new 700 system, but when SDPD multi-selects for a citywide broadcast the 800 system utilizes a separate frequency for each talkgroup patched. I doubt this is the efficient way (as far as radio channel usage is concerned) to accomplish this, (although it may be the easiest way on the console), but since it only occurs for very short periods of time, it probably usually isn't a problem.
Oooh, I have never seen that happen that way. All the multi-selects I've seen on Unitrunker both on the 700 MHz and 800 MHz city systems happen on a single voice frequency, and all the multi-selected talkgroups are all temporarily patched to one "supergroup" for the duration of the multi-select. If you switch over to the Patches tab you'll see all the multiselected talkgroups to the single supergroup, and then when they drop the MSEL all the talkgroups go away again. I never tested the theory back when I got to play with dispatch consoles, but I suspect the supergroup is either pre-programmed in the console or if they're adding talkgroups to an MSEL manually it might default to the first channel added being the "supergroup", because sometimes there doesn't seem to be any rhyme or reason to it otherwise.
 

Anderegg

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Wouldn't the multi-select protect the ability for a radio on a specific talkgroup to still key up and be heard by that talkgroup dispatchers headset, without having every police radio slaved to the same ATG at the same time? Can a radio evan talk INTO the system while receiving an ATG?

Paul
 

mmckenna

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Again, I don't know about modern P25 systems, but on the older SmartNet/SmartZone systems, it was a single talkgroup. It only used on traffic channel during transmission. It didn't take any more resources than any other traffic.
 

f40ph

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I seem to recall that an announcement TG was a separate TG which overrided any other TG. Something that you'd only use sparingly.
 

inigo88

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Wouldn't the multi-select protect the ability for a radio on a specific talkgroup to still key up and be heard by that talkgroup dispatchers headset, without having every police radio slaved to the same ATG at the same time? Can a radio evan talk INTO the system while receiving an ATG?
I’m not sure about that, because an ATG is different than a Multi-Select and I’ve never seen an ATG used on any of the SD systems. On Motorola Type II Smartnet systems, an All Call talkgroup had a status bit of ID+1, a Patch was ID+3 and an MSEL ID+7. Motorola Type II Smartnet - The RadioReference Wiki

I have never seen any All Call status bits on the city 800 MHz system or the old RCS (back when it was Smartzone), but I have seen plenty of patches and multi-selects.

As for the question about someone keying up during a multi-select or all call, I’m not sure what would happen, though I suspect the dispatcher would get the audio in their headset but it wouldn’t be repeated on the system since the dispatcher’s transmission is usually set up to take priority.

I was using MSEL and patch interchangeably in my previous post because they are both dispatcher initiated and both tie several talkgroups into one supergroup, and the resulting audio only takes up one voice frequency at a time on the system. In practice multi-selects are temporary when a dispatcher wants to make an announcement on several talkgroups at once (fire dispatches, PD checking citywide for a unit, etc), where as a patch will be initiated when they want to tie several talkgroups together to operate as one for a more prolonged period of time.

In this screenshot of a dispatcher’s elite console window, there are three MSEL and three patch tabs on the far right where either talkgroup patches or multi-selects can be initiated.
 

Jay911

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The ATG/Announce group on P25 is similar to the same kind of group on the old Smartnet/Smartzone systems.

A radio can have an announcement group established on its profile/personality. I say "can" - I have seen programming where no group is specified. If a group is specified, any transmissions on that group will override anything else the radio is receiving and be broadcast to the end user. The announce TG doesn't need to be programmed into a zone/channel slot on a radio; however if it is, that means the end user can transmit on that group too (in many cases in my experience, the announce TG is programmed into either only consoles or into consoles and chief officers' radios).

As for determining whether or not system XYZ is using it, I have found that SDRTrunk tracks the existence of the talkgroups. No other modern control channel decoding software I've used shows the data, but the data is of course in the control channel on any system. It's typically seen when a radio affiliates to a talkgroup. One such example from a system I monitor reads like this:

ACCEPT AFFILIATION GROUP: 2871 (GLOBAL) ANNOUNCEMENT GROUP:2719

That means that the radio in question is using 2871 as its tuned talkgroup, and the announce group/ATG is 2719.
 

wa8pyr

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Wouldn't the multi-select protect the ability for a radio on a specific talkgroup to still key up and be heard by that talkgroup dispatchers headset, without having every police radio slaved to the same ATG at the same time? Can a radio evan talk INTO the system while receiving an ATG?
When an Announcement Group is set up properly, radios on talkgroups which are part of the announcement cannot transmit while an announcement is being made, but likewise, the ATG cannot be used until no one is talking on any of the associated talkgroups. The only exception is dispatch consoles directly connected to the system; if they have preemption enabled, they'll override any transmissions currently in progress.

ATG has to be set up in both the system and subscriber radios; in the system, the ATG is defined, and the desired talkgroups assigned to it. It's similar but in reverse in a subscriber unit; a unique personality is set up with the desired talkgroups in it, and the ATG is placed in the appropriate field.

When transmitting on the ATG, one selects the ATG and the broadcast is sent to all talkgroups. You can also park your radio on the ATG and hear what's happening on all of the associated talkgroups, which gets pretty tiring; it does not work with scanners, however.
 
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