Driving to work this morning, my G4 was scanning an older Baltimore County scanlist that still had the old "NORTH" talk group listed. It seemed as though the Plectron two-tones were being sent over it. Is it possible that BCoFD is testing two-tone over P25 for potential replacement of 46.46mhz?
Baltimore County two-tone over P25?
- Thread starter ocguard
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Just an opinion/guess here, but I'd imagine it was just a simulcast of 46.46 and they just didn't mute the tones. A few trunked radio systems out in Western MD let the tones come thru over the main fire dispatch talk group, but don't use the trunking system as a two-tone alert system. If you look at Montgomery County, MD's new P25 Phase II system, they've all but gone away with two-tone dispatches from their original low band dispatch frequency and only use tone outs for specific purposes. Fairfax county, VA no longer alerts over the air as well as many other jurisdictions. I'd also bet they would eventually phase out the two-tone alerting system in the future as other newer CAD systems become available even with the volunteer departments.
ka3jjz
Wiki Admin Emeritus
Too as I understand it, two tone alerts are greatly distorted by a translation to P25....Mike
Appreciate the responses but…
1. seems odd that, after 30 years of NOT sending the zetron tones over the 800mhz, they would all the sudden begin without a reason
2. two-tone over P25 is emerging as a solution for voice paging when coupled with the unication G4/G5 pagers. Modern Third generation P25 vocoding has eliminated a great deal of the non-human distortion that plagued first generation vocoding and makes throughput very reliable for audible signaling.
3. Baltimore County is coming to a critical juncture with replacing the volunteer personnel alerting system, as the lowband transmitters are on borrowed time and low band pagers are nearing extinction. A very large geographical area of Baltimore county still relies heavily on volunteer fire stations. And the use of any primary alerting solution that relies on third party/commercial networks simply doesn’t meet the requirements from NFPA and ISO.
1. seems odd that, after 30 years of NOT sending the zetron tones over the 800mhz, they would all the sudden begin without a reason
2. two-tone over P25 is emerging as a solution for voice paging when coupled with the unication G4/G5 pagers. Modern Third generation P25 vocoding has eliminated a great deal of the non-human distortion that plagued first generation vocoding and makes throughput very reliable for audible signaling.
3. Baltimore County is coming to a critical juncture with replacing the volunteer personnel alerting system, as the lowband transmitters are on borrowed time and low band pagers are nearing extinction. A very large geographical area of Baltimore county still relies heavily on volunteer fire stations. And the use of any primary alerting solution that relies on third party/commercial networks simply doesn’t meet the requirements from NFPA and ISO.
I didn't think the Unication pagers use 2 tone over P25 anyway. They use a TG ID to trigger the pagers. At least that is how Unication shows them working. As for third Party alerting, I believe more departments are going that way regardless of NFPA.
You can use 2 tone on Unication and many departments are.
If they adopted 2-tone paging over P25, they would need to adjust their tone allocations as many current pairs will not work properly. I'm waiting to see what AACo does when their new P25P2 system comes online (at least for testing) later this year. Montgomery County dropped their 2-tone alerting shortly after transitioning to their P25P2 (Fire is still FDMA for most tgs,) which seems to be the trend. They still have a lot of volunteers, so I assume they are using a smartphone based system for personnel alerting.
I would be curious if you hear this again, as well as which talk group / control channel frequencies are involved.
Edit: I can confirm that I hear tones on BCoFD North Talk Group 9452 on a Unication G5. I guess its time to test out tone decoding!
When they are in their back up center, there is a lot of stuff that happens, that doesn't always stick around when they go back to their primary center, so yes, you may have heard tones going out from a patched talkgroup.
Anything is possible but I think this is for real. It would be a shame if its temporary. It is working and alerting like a pager. I also heard someone else was testing this for a while. I don't think it's a fluke but rather a beta test. At least I hope that is the case.
Is it working as it should? Decoding the tone you expect based on the dispatch? Maus92 makes a good point that two-tone over P25 requires larger tone separation than BCoFD's Plectron fast duo-tone code plan allows. I'm also surprised its alerting based on how little of the tones actually audible.
But I'm stoked that you have it working, and I hope BCo has something in motion. 46.46 needs to be taken out to pasture, despite the huge amount of nostalgia associated with it!
Testing has discovered that it really depends on the tones used. I've established two-tone over P25 for about 15-20 stations in my dispatch center's area of responsibility, and we had to screw around quite a bit to come up with pairs that would trigger radios. We've had success with getting several end user radios to recognize and trigger on tone sets, between Moto, Kenwood, and Unication devices.
This is working flawlessly for me 3 days in. Zero missed calls and zero falses. I’m already at the custom alert tone stage 
I hope this broadcast is intentional and here to stay because I can’t go back. Bye bye Minitor V. I loved you low band but I’m breaking up with you.
I hope this broadcast is intentional and here to stay because I can’t go back. Bye bye Minitor V. I loved you low band but I’m breaking up with you.There is best practices documentation out there that describes the tone pairs that work with P25 paging. I am not sure what tone pairs are currently used in Baltimore County, but perhaps they will be lucky and not have to change too many - if that is the plan. They would have to change out a lot of pagers, and FSA equipment, so it *seems* like we are seeing the first steps in that process. If it is an actual project, it could likely be found buried in the county's budget docs somewhere.
dpm797
Member
Worcester County uses both two tone paging over VHF and two tone paging over the P25 Fire Dispatch talk group. The Unication G5 pager does a great job of decoding and "opening up" when it is that pager/monitor mode.
My understanding is that all FSA equipment is now running on MachAlert or whichever SCADA-based medium BCoFD has gone to. The only thing paging controls is pagers now. So to create an entire new paging plan wouldn't be terribly burdensome.
Which tones are you monitoring on? Just curious. I have several friends at various volley houses around the county that want to try this out. I too am excited for the prospect. But the legend of 46.46mhz will be forever LOL!This is working flawlessly for me 3 days in. Zero missed calls and zero falses. I’m already at the custom alert tone stage
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