Announcement Talkgroups

[Spiffy50]

Hey guys, I'm trying to figure out how this works. Locally, a media outlet uses MCS2000 radios to scan the local police/fire
system. They have a channel labeled as "PEEL FIRE" which automatically picks up all of the dispatch talkgroups (there's I think theres 5 of them), but scan is NOT turned on with this mode. Any idea how this works? I asked, and the guy told me it was using an announcement talkgroup, but didn't know more.

[wavetar]

Basically, you can designate any talkgroup you wish within a personality as an 'announcement' group. Once you do so, when you sit on that announcement group, you will 'pick up' all the other 'regular' talkgroups programmed within that personality...so up to 15.

This is great for listening, however be aware that if you try & talk out on that talkgroup, the radio sends it as an 'announcement' group. This has no real affect unless it's been designated as an announcement talkgroup in the controller, but if you're trying to talk to others on that as a 'regular' talkgroup, they won't hear you. The receiving radios see that it's supposed to be an announcement, and if it's not set as the 'announcement' group in their programming, they ignore it, even if they're sitting on that talk group.

[d119]

So when sitting on the ATG, it's essentially forced scan.

[Spiffy50]

I tried programming in 10 talkgroups like this:

ATG in Trunking Personality was set to 001 (just a random TG). Inside the personality, the talkgroups are 101, 102, 103, 104, 105, 106, 107, 108, 109 and 110. In the Zone assignment, I entered the individual talkgroups as well as one called "ALL GROUP" which is set to ATG. When I switch over to the ALL GROUP on the radio, for some reason it will only receive talkgroup traffic on TG 104. Any idea why this would be?

[Spiffy50]

I read the radio in question from the media guy. The personality has Talkgroups 579 through 595 (odd numbers only). It has 597 set as its Announcement Talkgroup. In the Zone list, there's just one talkgroup with a label as "DISPATCH" that is the ATG (597). It receives all 15 TGs in the personality list. No matter how much tinkering I do, I can't replicate this with other talkgroups.

[wavetar]

I tried programming in 10 talkgroups like this:

ATG in Trunking Personality was set to 001 (just a random TG). Inside the personality, the talkgroups are 101, 102, 103, 104, 105, 106, 107, 108, 109 and 110. In the Zone assignment, I entered the individual talkgroups as well as one called "ALL GROUP" which is set to ATG. When I switch over to the ALL GROUP on the radio, for some reason it will only receive talkgroup traffic on TG 104. Any idea why this would be?

Is it perhaps a SmartZone system? If those talkgroups aren't affiliated with the site, you won't hear them. Just a thought.

[Spiffy50]

I'd thought about that as well, but firing up my scanner showed comms coming across on the other TGs in the personality that the (M) wasn't picking up. Another thought, on a newer ASTRO25 radio you can have (I think?) 50 TGs in a personality. Does this mean that in theory you could "scan" 50 talkgroups using this ATG method in one of those radios?

[Q2222A]

Announcement talkgroups (ATG) also known as "Multigroup" talkgroups are created, configured and managed at the system level of a Motorola Trunked Radio System. The Multigroup Talkgroup is created in the system and specific talkgroup IDs are added to the Multigroup as associated members. In the case of Smartnet systems, ATGs are managed in the Subscriber Access Control (SAC) database. In the case of Smartzone 2.05, 3.0 and 3.5OL systems, the ATGs are managed in the SmartZone Manager. In the case of Smartzone 4.1 and ASTRO P25 systems, the ATGs are managed in the User Configuration Manager (UCM).

Subscriber units and consoles are merely users or participants in an announcement group. The subscriber cannot create an ATG group. If you program your radio for a particular ATG ID, you will be able to hear only the traffic of talkgroups assigned as members of the ATG in the system. If you transmit on an ATG, all talkgroups that are members of the ATG will hear you. Normally, individual IDs must be granted specific permission to transmit on ATG talkgroups in the system.

I hope that helps,

Dennis

[Spiffy50]

It does indeed, and certainly answers a few questions. Thank you! It certainly makes sense that the above radio I saw works to "scan" fire talkgroups as I would imagine the system administrator saw the possible need to transmit to everyone on those groups at the same time, thus the ATG trick works for receiving them.

[Spiffy50]

I put some thought into this and have a question. How does the subscriber unit know what groups the system administrator has entered in as part of the ATG? That information is not sent over the air. When an announcement talkgroup is sent out, a regular group call channel grant OSW is transmitted. There's also no OSW specified for such a thing, as call setup would take too long. If there are 15 talkgroups in an ATG, it would need to send out double OSWs for each, which is 30 OSWs. Since a Motorola radio won't act on a single OSW (it must receive it correctly twice before it acts on it), that could take some time on a busy system.

I guess what I'm getting at is how does the subscriber radio "know" that a given talkgroup(s) are part of the announcement talkgroup, isn't that why the ATG ID gets programmed in the trunking personality? From what wavetar had posted in previous, the radio will treat every talkgroup contained in the TG list for that given personality as belonging in the announcement. In that scenario, if all police talkgroups were in the same personality, the dispatcher could easily send out a message to all police units regardless of what TG they were on. A multiselect/patch would do the same but could take too long to setup. A pre-defined ATG would take care of that pretty easily.

Does someone have a copy of a trunked system manual describing exactly how one is set up and the particulars?

[wavetar]

Normally, you build a 'multi-group' list in the controller using the 'affiliate' command. You designate the 'announcement' group, and list all 'regular' talkgroups which you wish to be 'affiliated' with it. The primary reason for this list is so if someone tries to initiate an announcement, the controller first checks this list & if there are currently conversations going on in the system on the regular talkgroups which are affiliated with the announcement group, the controller will give a busy to the ATG initiator, and will begin 'locking out' each of the affiliated talkgroups as they stop talking...they won't be able to access the system, getting a busy as well. Once all affiliated talkgroups have been locked out, the ATG radio gets the talk permit tone & can then make the announcement. This ensures everyone that is supposed to hear the announcement does hear it. It can be set to work in slightly different ways, but that's the method I'm familiar with.

This list is completely independent of what's programmed into subscribers, and there's no limit to how many affiliated talkgroups you could have (I'm sure there is, but it's a high number & I don't know what it might be). The subscriber has no way of knowing what talkgroups are in the controller list, it only knows what's programmed into it's personalities. This is why 'normally' the radio can listen in on whatever talkgroups are programmed into it's personality when sitting on the ATG...it assumes they are all part of the ATG list. I don't know why yours isn't doing this in your case.

Unless I'm missing a piece of the puzzle...it has been 6 years or so since I messed with these parameters in a system, so that's possible.