Motorola OSWs

[slicerwizard]

Originally Posted by fpo701

Guys,

A while ago, I posted a few questions on the trunking forum about how to decode Motorola control channels. I finally have a radio (396XT) in my hands and can kind of see what's going on. I wrote a quick little program to dump the control channel data to a file.

Now I have questions. Let me start with some basic terms.

1) affiliate. When does an affiliate message appear? In the real world, what caused it? I think this is what happens when a radio wants to "scan" a particular TG.

Technically, what your scanner sees on the outbound control channel is actually the system acknowledging an affiliation sent by a radio, but it's convenient and accurate enough to call it an affiliation command. Radios affiliate when they start monitoring a site's control channel (e.g. the radio was just turned on, or the radio just roamed from another site, or the radio had been on a conventional channel and the user switched to a trunked talkgroup), or when the user switches from one talkgroup to another, or when the system tells the radio to affiliate.

Put another way, can I use this to see what TGs a particular radio is scanning? If my definition is correct, does the radio re-affiliate if he changes to a different zone (bank) on the radio?

"Scanning" implies monitoring multiple talkgroups simultaneously; affiliations and scanning do not relate to each other. An affiliation tells you the specific talkgroup the user has selected via the zone/channel controls.

2) patch. Is this two TGs patched on the same system, or different systems? Am I way off on the meaning?

Patch OSWs announce the joining of two or more of a system's talkgroups. Patches between separate systems do not generate patch announcements.

3) difference between affiliation and affiliation request?

Affiliations have already been covered. An affiliation request is generated by the trunking system when it wants to know what site (more properly, what zone) a radio is monitoring and what talkgroup the user has selected. A radio will respond to an affiliation request by affiliating.

The reasons for issuing an affiliation request:

- on a SmartZone system, a radio has generated no traffic for 4 hours; if the radio is no longer monitoring (e.g. battery died, etc.), there is no need to send voice traffic for whatever talkgroup that radio was monitoring to that zone if no other radios on that zone are affiliated to that talkgroup. The affiliation request will only be broadcast on the last zone the radio was seen on. If the radio responds by reaffiliating, the site will continue carrying audio for the talkgroup the radio is monitoring for an additional 4 hours. As long as the radio keeps responding to affiliation requests, the cycle will repeat every 4 hours. A portable radio left on in a charger or a base radio left on overnight will trigger these repeated affiliation requests.

- on a SmartZone system, a trespassing radio (e.g. a radio from some other trunking system) has affiliated to the system and then said "Oops, my bad - this isn't my system; gotta go - bye" and now the system needs to know where its authorized radio is and what talkgroup it's monitoring. This request will be broadcast on all zones.

- a radio is requesting a voice channel grant, but hasn't told the system what talkgroup it is using. When a user presses the PTT button, the radio just tells the controller "I'm the radio using RID xxx and I want to talk to my group"; the talkgroup number is not included in the request. Normally, this isn't a problem, since the system remembers the last talkgroup the radio affiliated to. However, if the user has just powered on the radio and then quickly keyed up before the radio has had time to affiliate, the radio may fail (depends on the radio/firmware) to tell the system what talkgroup it is on.

- someone in a supervisory position tells the system to ping the radio. This can be used to figure out which zone a radio is in and what talkgroup it is monitoring. Repeated pings can be used to track down a lost or stolen radio.

4) SlicerWizard gave two examples for what look like the same command, but two different meanings:
308 G 4032 SysID; SysID=4032 ctl chan=CC
30B G 28CC

308 I 0CA5 Affiliation request; RID=CA5
30B I 261B

Those are separate commands; the former broadcasts the system's ID (SysID) and the current control channel frequency index. Radios use it to verify that they are monitoring the correct system, e.g. not trespassing. The ten low order bits of the last value (28CC) define the CC index, so the actual value seen can range from 2800 to 2BFE.

The 308/30B dual-OSW that ends with 261B is an entirely different command, as noted. If it ended in 261C, it would mean something else yet again.

5) The systems I tested with seem to use different commands from slicerWizard's example:
309 I 12CB Affiliation; RID=12CB TG=104
310 I 104A

On my system:
308 I 12CB Affiliation; RID=12CB TG=104
310 I 104A

Non-SmartZone systems probably only use the 308/310 version. Some SmartZone systems use 308 and some use 309.

I never see a 309. The systems I am monitoring are Akron and Barberton in Summit County, OH.

Non-SmartZone.

Thanks,
Frank

No prob.

[fpo701]

Originally Posted by slicerwizard

The 308/30B dual-OSW that ends with 261B is an entirely different command, as noted. If it ended in 261C, it would mean something else yet again.

Great. Does the source for trunker deal with all the different flavors of the 308/30B combination? That might help me a lot.

[wayne_h]

Originally Posted by fpo701

Great. Does the source for trunker deal with all the different flavors of the 308/30B combination? That might help me a lot.

No, it doesn't. Just 0x30B on its own has so many variations based on the address information paired with it. There are the various rejection codes, affiliation request types, SZ site announcements.....

[wayne_h]

Originally Posted by slicerwizard

Non-SmartZone systems probably only use the 308/310 version. Some SmartZone systems use 308 and some use 309.

And a good example of how Motorola will take previously defined OSW commands and reuse them. Since Type I/IIi isn't used with SmartZone systems they've used it for a specific type of affiliation. Previously it was used for IIi signaling.

[fpo701]

Quick question related to patches. I've been monitoring (not the control channel data) Summit County 800 (RRID 2707) with nothing programmed in. The 396XT displays patches. I have seen two talkgroups patched. When one side is used, both numbers show. When the other side is used, only the one number is displayed (twice).

Ex:
32016 36848 (SO Disp1 to South OPS)
36848 36848 (South OPS only)

From the radio users point of view, what are they seeing/doing? Is the SO radio on SO Disp1, unaware he is actually on South OPS?

[slicerwizard]

Originally Posted by fpo701

From the radio users point of view, what are they seeing/doing?

Radio users don't see anything; their radios just display the talkgroup that they're dialed to.

Is the SO radio on SO Disp1, unaware he is actually on South OPS?

His inbound comms are on Disp1, but the system broadcasts it on South ops.

Users are often aware that several channels (talkgroups) have been joined, but they don't know which one is the supergroup, nor would they even be aware of such a concept.

[wannabescannist]

May be an odd question, but can there be a supergroup that includes all talkgroups? Like a system-wide broadcast? If so, is this concept even used in practice (if the answer is yes, on large state-wide systems, won't that put a huge strain on the network)?

[wayne_h]

Originally Posted by wannabescannist

May be an odd question, but can there be a supergroup that includes all talkgroups? Like a system-wide broadcast? If so, is this concept even used in practice (if the answer is yes, on large state-wide systems, won't that put a huge strain on the network)?

Yes, it's called a system-wide broadcast. It's TG FFF or 65520.

Here's the hierarchy:
Network-wide (SZ or AMSS)
System-wide (or Site-wide if SZ)
ATG aka MultiGroup
Talkgroup
Individual

Patches and MultiSelects are their own thing. The term "supergroup" is more a technical term to describe the OSW portion of a patch or MSEL.

[DiGiTaLD]

Originally Posted by wannabescannist

(if the answer is yes, on large state-wide systems, won't that put a huge strain on the network)?

Don't see why, I would think it would only require one voice channel at every site on the system to do it. Its not like it's a console multiselect where it requires one channel for every seperate group selected.