DSDPlus Emerg Private Call

[RaleighGuy]

Scrolling through the local P25 voice channels and came across two channels that were displaying Emerg Private Call, with no sound. Does anyone know what these transmissions are from, and if actual emergency buttons why they weren't cleared out? I did not notice this on UT v2 which was running on a different computer at the same time.

 

[Reconrider]

Emerg button calls are basically a priority call and anyone talking is cut off so said radio can have priority. DSD also doesn't "clear" the events activity since it's only logging what it has seen. You can always remove it from the event log file if you really want to, but it's not going to do much for you. Most times they are pressed, it's by accident

 

[hruskacha]

Since Target and Source are both RID's, I assume its an individual call (unit to unit), and both radios have encryption because its a private call. And on top of that an emergency button was pressed. But a "pri7" emergency call? it should be "Pri1"? That's what I don't understand.

 

[a417]

Do those RIDs correctly map out to a unit(or unit range)? I have seen decoding errors decode as spurious private calls, this could be similar.

 

[slicerwizard]

OP was sitting on a P25 traffic channel, not a control channel. Some Motorola systems frequently send messages on those channels that look like private call link control messages: Link control opcode #3, LC_UU_V_CH_USR Unit To Unit Voice Channel User.

So it's effectively just garbage.

 

[RaleighGuy]

Since Target and Source are both RID's, I assume its an individual call (unit to unit), and both radios have encryption because its a private call. And on top of that an emergency button was pressed. But a "pri7" emergency call? it should be "Pri1"? That's what I don't understand.

A private call does not mean encryption, it means radio to radio rather than to a TG

 

[RaleighGuy]

Okay, revisiting this subject as it is continuing on one frequency on the Cary/Wake County TRS. The frequency has a strong continuous carrier, like a control channel but it is not listed as one, the SRC and TGT are not standard radio IDs on the system. According to Unitrunker that frequency has about 780K hits, not a control channel, and is capable of receiving voice, data, and secure traffic.

What I'm wondering is if maybe these are the MDT transmissions between the unit and servers and DSD+ is mistakingly labeling/decoding them as Emerg Private calls? Anyone have any guesses?

 

[GTR8000]

ASTRO 25 data channel. Very common on those systems. Often it maintains a constant carrier during busy periods so that the repeaters aren't constantly keying/dekeying for quick data bursts. Makes things more efficient. And no, it's normally not MDT traffic, but rather GPS/AVL between the APX subscribers and the system. Could also be used for POP25 if the system is provisioned with over-the-air programming.

 

[RaleighGuy]

ASTRO 25 data channel. Very common on those systems. Often it maintains a constant carrier during busy periods so that the repeaters aren't constantly keying/dekeying for quick data bursts. Makes things more efficient. And no, it's normally not MDT traffic, but rather GPS/AVL between the APX subscribers and the system.

Thank you for that explanation.

 

[GTR8000]

If you watch the activity in UT 2.1, you should see that channel LCN/frequency change color in the active calls grid (default is orange, I believe), indicating that channel is keyed up for data traffic. You'll also see quick flashes of activity with Dat in the Service column, and the Target fields populated with the Subscriber ID (not a Talkgroup ID as normally appears in the Target fields). If you look at the Properties tab of the site, the Data field will display Autonomous and by Request if the data channel is keyed up, otherwise it shows Request Only.

 

[RaleighGuy]

If you look at the Properties tab of the site, the Data field will display Autonomous and by Request if the data channel is keyed up, otherwise it shows Request Only.

Yes, it is actually flashing between the two labels on the property tab. Never noticed that before. Also, looking at the frequency on the calls tab, it actually displays the actual RID, rather than either the SRC or TGT DSD+ shows, along with DAT.