Trunking (Analog or Digital) Voice Pagers

[WuLabsWuTecH]

So there isn't currently a voice pager on the market that can handle trunking and alerting like a minitor does. But I am wondering, why not? I have an engineering background and I was thinking that if a Uniden scanner can sit on a talkgroup, and a Uniden scanner can decode tones, then certainly taking the next step to sitting on a talkgroup and decoding tones isn't that far of a jump is it?

I figure that if you don't need all the bells and whistles of a full motorola radio or a full scanner, you could probably fit all of the electronic components into a smaller case the size of a minitor right? And program it to sit on a Talkgroup and listen for tones, and open the squelch when it hears the right set of tones? Clearly I'm missing something because it can't be this easy or else it would be done already. But all the departments I know that have gone to 800 MHz all simulcast onto VHF or Low Band to activate minitors, and then then sit a base station radio on a special talkgroup (e.g. Station 123 Page) which is patched to the dispatch TG when that station is needed.

It seems like building a smaller circuit board and sticking it inside a minitor sized case would be a more cost effective measure? And if they can sell Uniden Scanners for about $300, I would assume you could build a pager and sell it for about the same right?

The only reason I can think of that it hasn't been done is that most systems are eventually going to move toward digital and since digital systems can't do toned paging (because of the signaling mechanism where the tone is not technically continuous and therefore would be very hard to decode) no one wants to build one to fill the gap of a decade or so before digital will be the norm?

 

[cdknapp]

Unication is currently it the R&D phase of their G3 (P25/conventional) and G4 (P25/Trunking) pagers at this point. I believe that beta testing should begin soon on these pagers. It looks like they are the only manufacturer that has any interest or is doing anything outside of the current technology (analog) presently on the market.
Keep your eyes opened; should become interesting.

 

[RBMTS]

No paging is done through a trunking system with exception of Unit ID paging (which is not a tone page). The main reason being that QCII paging is not only measured by tone frequencies but also timing of the tones themselves. If you have a trunking system with many different frequency sets, the pager would need to evaluate what is an actual tone as compared to what could be a tone of a person just starting to talk (example if you said "ahhhhhh" over the air) . The time to analyze that audio of that frequency and then move on to scan other frequencies would then throw off the timing of an actual paging signal once it has started to be received.

Secondly we all know that all new trunking systems will be digital. Ever listen to a alert tone being transmitted on a digital frequency? The characteristics of the actual tone are way off from the original tone to to the A/DA conversion. There is no way it could be usable as a QCII tone.

I'm sure you are aware but I will make note just in case - the Uniden scanners do not do FTO on a trunking ID. The FTO will only work on a single conventional analog frequency. Again, you probably knew that but I wasn't sure by way of your description above.

Great concept you had. It's been discussed before on many threads. It just isn't going to work.

Now what would be cool is if there was a pager that could work as a trunking receiver and listen to the paging code for an ID. Now that might be worth while.

 

[RBMTS]

Unication is currently it the R&D phase of their G3 (P25/conventional) and G4 (P25/Trunking) pagers at this point. I believe that beta testing should begin soon on these pagers. It looks like they are the only manufacturer that has any interest or is doing anything outside of the current technology (analog) presently on the market.
Keep your eyes opened; should become interesting.

Interesting information. I'm wondering how that would be done. Try measuring audio tones via a trunking system, they change dramatically. I'm wondering if the concept is that a trunking system will need to dedicate one frequency pair that is not in the normal voice channel assignments and that frequency can be used for paging.

Time will tell when more info is released.

 

[cdknapp]

Interesting information. I'm wondering how that would be done. Try measuring audio tones via a trunking system, they change dramatically. I'm wondering if the concept is that a trunking system will need to dedicate one frequency pair that is not in the normal voice channel assignments and that frequency can be used for paging.

Time will tell when more info is released.

They initially started work on the (digital P25) conventional side, and then migrated towards trunking as well. We can only imagine the amount of R & D that they are putting into these projects.
Their U3 portable (already in beta testing) does analog, P25 and some DMR, and I understand that it will be doing full DMR (Trbo) as well very soon, all in ONE radio. They are working on trunking capability with these as well, and that’s not too far out from what I understand.
In consideration of everything that they are doing, I have faith in their capabilities. Makes sense; if you’re working one project, what not go all the way (two way and paging)?
And you know that market will be there – already has a good start with all the new systems going up.

I agree, time tells all. I will post more information as it becomes available, so stay tuned.

 

[WuLabsWuTecH]

No paging is done through a trunking system with exception of Unit ID paging (which is not a tone page). The main reason being that QCII paging is not only measured by tone frequencies but also timing of the tones themselves. If you have a trunking system with many different frequency sets, the pager would need to evaluate what is an actual tone as compared to what could be a tone of a person just starting to talk (example if you said "ahhhhhh" over the air) . The time to analyze that audio of that frequency and then move on to scan other frequencies would then throw off the timing of an actual paging signal once it has started to be received.

Secondly we all know that all new trunking systems will be digital. Ever listen to a alert tone being transmitted on a digital frequency? The characteristics of the actual tone are way off from the original tone to to the A/DA conversion. There is no way it could be usable as a QCII tone.

I'm sure you are aware but I will make note just in case - the Uniden scanners do not do FTO on a trunking ID. The FTO will only work on a single conventional analog frequency. Again, you probably knew that but I wasn't sure by way of your description above.

Great concept you had. It's been discussed before on many threads. It just isn't going to work.

Now what would be cool is if there was a pager that could work as a trunking receiver and listen to the paging code for an ID. Now that might be worth while.

Well my point is that it wouldn't be a scanner. It would sit on one frequency like Minitors do (or possibly scan a second). And the reason it's not done by tones *I thought* was because there was no pager out there that can decode it. In our system, we actually have some older departments with stations that retain their old tones before their dispatch, but it's not decoded. They sit their radios on "OLDER FD DISP" and the tones play before the voice. It's really just an attention grabbing mechanism and I guess they decided to keep it since everyone was already conditioned to it.

And, yes I know that FTO doesn't work on trunked, but I'm not sure WHY. Like I said, it can do FTO and it can sit on a single TG on trunked. (It also has to sit on a single frequency for conventional, it can't scan when in FTO mode) So why can't it sit on a single TG on trunked.

And yes, I took a digital signaling class and i know that tones sound very different on a digital system. Because of the way the signal processing works, I was under the impression that it was impossible to decode tones with the decoding technology as we currently know it. Because when you go to digital, there is technically a degradation of signal since you can only modulate in quantized amounts. That is, think of a staircase instead of a smooth curve. And in order to decode, you would have to have some sort of integrator that could take the staircase and approximate it back into a curve. Which is doable, but unless someone has already come up with an algorithm I don't know of (maybe Unication?) there is no way to get it to re-construct the original signal reliably every time.

The only way I can think of around this would be to allow for wide tolerances in tone decoding, but that would mean that you would have to set tones further apart on the spectrum such that my department's tones won't accidentally set off your department's pagers.

 

[n5ims]

Without doing any real analysis, I don't see why a digital pager wouldn't work on a trunking system if it was done using somewhat different notification methods. Instead of the tone system currently in use (which I can see why that wouldn't work due to sampling issues, etc.) I believe that using the digital nature of the system they could simply send out a series of digital signals (something like 0x 25f94b7, 0x 4e27b94a - note, 0x is simply an indication that the following text is a hexadecimal number) as a code to activate the pager and then a text message (also digitally encoded) as the message. With a talkgroup dedicated to paging, there would be no "falsing" or unwanted noise on a standard voice channel.

Now the pager would need extra horsepower and circuitry to handle trunking (e.g. monitoring the control channel for its talkgroup and switching to the assigned channel that talkgroup would use for that transmission and return to the control channel once the transmission is complete) and would therefore be a much more expensive device than the simple analog or even the digital ones currently in use that only have to monitor a single frequency.

 

[APX7500X2]

It would use call alert on the trunking system. Our department does it for our trunking portables now as an alert mode. Radio sits on the alert talk group and when they want us they group alert the radios.

Its been done for years and years, its just trunking portables are a lot of money. You could make a pager do it easy, how much would be the question

 

[krokus]

I like the sounds of this project.

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[captaincab]

And i am sure Unication will charge a crazy amount of money for this capability like they did with their pagers. And how are smaller fire companies going to afford it ? My dept pays under 225 for refurbished minitor 4's and sometimes min5's and under 150 for minitor 2s there is no way we can afford the 450 to 500 dollar plus price Unication would be charging lucky for us we are on and planning on staying on a analog 500mhz radio system in our county except for the dispatch channel which is lowband with a uhf simulcast channel.

 

[KAA951]

Two ideas-

My first idea on this is- why can't the pager simply be programmed to one of the frequencies used by the trunking system. When a dispatcher wants to tone out, the system controller could recognize that and key up the designated paging transmitter in the system. (eg- if 866.100 was the paging freq the pager would monitor that 24/7, but that freq could be used for other purposes on the trunking system when it isn't paging. Once the page is selected, the 866.100 transmitter is grabbed by the controller and held until the page is done- once it is no longer being used to page it goes back into que). As far as the pager would be concerned, it would be just like it was operating in a conventional mode, so it would keep pager costs lower and even work with some existing equipment in VHF trunking systems.

The other idea is, why don't they design a pager that detects and monitors the 9600 baud data stream of the P-25 system? The pager could be tripped by a digital messaging signal and be designed to do text to voice- or do both text and voice for calls. Our agency played with piggybacking on the 9600 baud stream for mobile data terminals- and it worked fine for text messages and using CJIS... Just not broadband apps like images.

This discussion kind of reminds me of the one a few years ago bemoaning the fact that there were no dual band commercial radios on the market for public safety! Now look where we are!

 

[krokus]

My first idea on this is- why can't the pager simply be programmed to one of the frequencies used by the trunking system. When a dispatcher wants to tone out, the system controller could recognize that and key up the designated paging transmitter in the system. (eg- if 866.100 was the paging freq the pager would monitor that 24/7, but that freq could be used for other purposes on the trunking system when it isn't paging. Once the page is selected, the 866.100 transmitter is grabbed by the controller and held until the page is done- once it is no longer being used to page it goes back into que). As far as the pager would be concerned, it would be just like it was operating in a conventional mode, so it would keep pager costs lower and even work with some existing equipment in VHF trunking systems.

The logic for that is possible, but adds unnecessary complexity. Added to that, there are a couple of other reasons that I can think of: 1) Delays in tone-out, due to that frequency being busy. (Added complexity in the control circuitry.) 2) Limited range of 800 MHz, creating more issues on a multi tower systems.

The other idea is, why don't they design a pager that detects and monitors the 9600 baud data stream of the P-25 system? The pager could be tripped by a digital messaging signal and be designed to do text to voice- or do both text and voice for calls.

Once again, complexity involved in monitoring the control channels, especially in a multi tower system.

our agency played with piggybacking on the 9600 baud stream for mobile data terminals- and it worked e!

How did you piggyback a trunked system?


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[SCPD]

My first idea on this is- why can't the pager simply be programmed to one of the frequencies used by the trunking system?

You want to interrupt a call already in progress on that channel?

Personally, I think voice paging is obsolete. Text is better. Critical information (like an address) is right there. You don't need to write it down.

 

[captaincab]

My cellphone text alert won't wake me up but my minitor pager will even without being in a amplifed charger. Just saying.

You want to interrupt a call already in progress on that channel?

Personally, I think voice paging is obsolete. Text is better. Critical information (like an address) is right there. You don't need to write it down.

 

[krokus]

Personally, I think voice paging is obsolete. Text is better. Critical information (like an address) is right there. You don't need to write it down.

Voice allows you to receive updates; pass more info than can be put in a text; and is not against the law to check, while behind the wheel, like is common.

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