Before a fire dispatch they have a few beeps, I don't think it's for paging, I think just attention. They also have a beep everyonce in awhile in the police channel during restricted traffic. I cannot hear those using OP25, interested to know how I might get that to work?
On Sun, Apr 29, 2018 at 1:06 PM, nokoa3116@gmail.com [op25-dev] op25-dev@yahoogroups.com wrote:
Before a fire dispatch they have a few beeps, I don't think it's for paging, I think just attention. They also have a beep everyonce in awhile in the police channel during restricted traffic. I cannot hear those using OP25, interested to know how I might get that to work?
How do you know that they are sent? What's the duration?
My local fire dispatch sends some data bursts and paging tones on the old VHF FM repeater for major incidents, but they do not get sent on new the P25 system (yet they are linked for voice traffic). I'm actually not sure how/if they do paging with the P25 system.
Also, possibly depending on your hardware and other factors, there could be a bit of delay before op25 starts decoding audio, so if the tones are really short (a few hundred milliseconds), they might get missed....
~iain
I can hear them on the BCD436HP scanner and the online feed. OP25 hears them but it just doesn't play them properly, I sometime hear like two noises that sound kind of like, kkkt kkkt very low. I think that they are long enough for it to decode.
Our P25 phase 2 system is still in transition - most P25, some analog - all simulcast. Fire tones that go over the P25 are simply a result of them not being kept off there. There is no decoding done on digital channels because it doesn't work. Our tones will eventually move to a high band analog channel (they are still low band for decoding).
Chuck
On 4/29/2018 4:21 PM, iain macdonnell - N6ML n6ml@dseven.org [op25-dev] wrote:
On Sun, Apr 29, 2018 at 1:06 PM, nokoa3116@gmail.com [op25-dev] op25-dev@yahoogroups.com wrote:
Before a fire dispatch they have a few beeps, I don't think it's for
paging, I think just attention. They also have a beep everyonce in awhile in the police channel during restricted traffic. I cannot hear those using OP25, interested to know how I might get that to work?
How do you know that they are sent? What's the duration?
My local fire dispatch sends some data bursts and paging tones on the old VHF FM repeater for major incidents, but they do not get sent on new the P25 system (yet they are linked for voice traffic). I'm actually not sure how/if they do paging with the P25 system.
Also, possibly depending on your hardware and other factors, there could be a bit of delay before op25 starts decoding audio, so if the tones are really short (a few hundred milliseconds), they might get missed....
~iain
Sounds like OP25 doesn't fully implement IMBE tone frame decoding and audio synthesis.
At 04:06 PM 29-04-2018, nokoa3116@gmail.com [op25-dev] wrote:
Before a fire dispatch they have a few beeps, I don't think it's for paging, I think just attention. They also have a beep everyonce in awhile in the police channel during restricted traffic. I cannot hear those using OP25, interested to know how I might get that to work?
Posted by: nokoa3116@gmail.com
Do the tones not go like voice over radio. Is it like a code that the scanner then changes into a beep?
Same here. I can hear our tones on the high band. I think it depends on how the core is sending them.
From: op25-dev@yahoogroups.com op25-dev@yahoogroups.com Sent: Sunday, May 20, 2018 10:36 AM To: op25-dev@yahoogroups.com Subject: [op25-dev] Re: Why can't I hear fire tones?
Do the tones not go like voice over radio. Is it like a code that the scanner then changes into a beep?
My take is that any paging tones that one happens to hear over P25 systems is because the system is simulcasting an analog channel that carries them. That's what is happening in my county. As soon as the P25 is 100% switched over, the fire paging will only go out over an analog channel. Tones sent over a digital system (P25 or other) do not decode reliably - the codec doesn't handle a tone well and the frequency ends up getting shifted.
Chuck
On 5/20/2018 2:15 PM, zlatiolais@yahoo.com [op25-dev] wrote:
Same here. I can hear our tones on the high band. I think it depends on how the core is sending them.
*From:* op25-dev@yahoogroups.com op25-dev@yahoogroups.com *Sent:* Sunday, May 20, 2018 10:36 AM *To:* op25-dev@yahoogroups.com *Subject:* [op25-dev] Re: Why can't I hear fire tones?
Do the tones not go like voice over radio. Is it like a code that the scanner then changes into a beep?
At 11:35 AM 20-05-2018, nokoa3116@gmail.com [op25-dev] wrote:
Do the tones not go like voice over radio.
Generally, no.
Is it like a code that the scanner then changes into a beep?
Yes. Tone frames encode a frequency index and a volume level. A receiver has to synthesize the indicated tone/volume for 20 ms per frame.
Page 20 has a list of AMBE tones:
A slightly different list is found on page 58 here:
http://dvsinc.com/manuals/AMBE-2020_manual.pdf
IMBE tone frames are likely similar.
--
Okay, thank you for the information, this helped me understand a little more. But how would I go about implementing this into op25 so the tones could be heard?
You would have to separately listen for the tones on the highband system. The way the sitecontroller works is when the dispatcher clicks the screen for toneout the site controller bypasses the 800/700 system and routes straight to the highband transmitter. You will never get it unless they push a data packet to 80/700 radios that have the feature. So far I haven’t seen it deployed to any sites that I work.
From: op25-dev@yahoogroups.com op25-dev@yahoogroups.com Sent: Monday, May 21, 2018 11:37 AM To: op25-dev@yahoogroups.com Subject: [op25-dev] Re: Why can't I hear fire tones?
Okay, thank you for the information, this helped me understand a little more. But how would I go about implementing this into op25 so the tones could be heard?
Here are the fire tones I hear on a Uniden Scanner. I am not sure if it actually goes to a separate frequency just for the tones, but to me it doesn't sound like it. https://soundcloud.com/nokoa-official/sets/fire-tones https://soundcloud.com/nokoa-official/sets/fire-tones
What exactly are you trying to determine about the tones? They appear to be “Alert” tones sent by the dispatch operator ahead of the voice message. I don’t think they actually serve as a signaling function as would commonly be found in analog paging systems.
I believe that someone has already stated that there are only a handful of specific tones or tone combinations that are provided for in the P25 vocoder. Any other tones or tone combinations transmitted into the speech input of the vocoder quote likely will not reproduce and exact replica as the source tone(s) primarily because the vocoder is designed to encode and compress speech.
Bill, WA8WG
From: op25-dev@yahoogroups.com [mailto:op25-dev@yahoogroups.com] Sent: Saturday, June 16, 2018 2:58 PM To: op25-dev@yahoogroups.com Subject: RE: [op25-dev] Re: Why can't I hear fire tones?
Here are the fire tones I hear on a Uniden Scanner. I am not sure if it actually goes to a separate frequency just for the tones, but to me it doesn't sound like it. https://soundcloud.com/nokoa-official/sets/fire-tones
I figured they may not have been used for paging, I didn't know what to call them. The problem is I cannot hear those alert tones on OP25 and can't understand how I may fix it on OP25. They are quite important for listeners, as they get the listener's attention when a new fire call comes in.
I don’t think there is an easy answer because op25 uses a software vocoder written to decode speech as opposed to commercial P25 radios that employ the DVSI chips that were revised and redesigned to pass tone signaling, DTMF, Knox and single tone. If it’s important to your application to pass the tones to the listener then you should consider using a commercial radio or scanner that doesn’t affiliate or cause unwanted transmission on the public safety communications system of interest.
There are a number of surplus p25 radios that could be used to accomplish this task. The major fly in the ointment would be if your system is a Phase-II system that would require a must more costly alternative. Perhaps one of the active programmers that regularly contribute to op25 will jump in here to do a better job of explaining the software vocoder in P25 that I am capable of doing.
Lastly, I gather that your Uniden scanner passes the alert tones, so is there a reason that you can’t use it or a similar receiver for your application?
Good luck,
Bill
From: op25-dev@yahoogroups.com [mailto:op25-dev@yahoogroups.com] Sent: Saturday, June 16, 2018 3:31 PM To: op25-dev@yahoogroups.com Subject: [op25-dev] Re: Why can't I hear fire tones?
I figured they may not have been used for paging, I didn't know what to call them. The problem is I cannot hear those alert tones on OP25 and can't understand how I may fix it on OP25. They are quite important for listeners, as they get the listener's attention when a new fire call comes in.
OP25 works great in my city while all p25 p2 scanners that I tried don't do well at all, and constantly miss transmissions. I tried BCD436HP 996 and now SDS100. I understand what you mean software wise. Just curious if I can modify the vocoder on OP25 to make it work.
Do you know if your p25 system is a simulcast (LSM) or not? Sometimes you can improve the reception of simulcast systems when using a consumer grade receiver not specifically designed for simulcast by using a highly directional (Yagi) antenna aimed at one of the transmitter sites nearest your location. This doesn’t always work if there is very strong overlap between the various transmitters in the network but is worth a try as the antennas are not all that expensive.
Bill
From: op25-dev@yahoogroups.com [mailto:op25-dev@yahoogroups.com] Sent: Saturday, June 16, 2018 4:02 PM To: op25-dev@yahoogroups.com Subject: [op25-dev] Re: Why can't I hear fire tones?
OP25 works great in my city while all p25 p2 scanners that I tried don't do well at all, and constantly miss transmissions. I tried BCD436HP 996 and now SDS100. I understand what you mean software wise. Just curious if I can modify the vocoder on OP25 to make it work.
The system I monitor is http://www.radioreference.com/apps/db/?sid=7804 each site transmits on a different frequency.
OK. I see that it’s a Phase II system but is not simulcast. I am wondering why you’re missing some of the transmissions? Have you checked to make sure the firmware in the scanner(s) that you’ve tested or are using have the latest and greatest firmware? Being that the system is Phase-II leave out any possibilities of using something like an XTL5000 or and XTS5000 radio. You’d have to up the radio and that could get costly.
Maybe someone know of a Kenwood, Yaesu, or Icom radio that does Phase-II that may make a good non-affiliating receive only receiver? A Motorola APX would be pricey.
Good Luck,
Bill
From: op25-dev@yahoogroups.com [mailto:op25-dev@yahoogroups.com] Sent: Saturday, June 16, 2018 4:29 PM To: op25-dev@yahoogroups.com Subject: RE: [op25-dev] Re: Why can't I hear fire tones?
The system I monitor is http://www.radioreference.com/apps/db/?sid=7804 each site transmits on a different frequency.
The vocoder used in op25 is open source so anyone can modify it. Trouble is, unless you are well versed in DSP techniques and in particular the IMBE/AMBE codec the learning curve is going to be a big mountain to climb.
Right now ambe synthesized tones are not handled. See ./lib/ambe.c and more specifically mbe_dequantizeAmbeParms()
Some jurisdictions pass tones as audio on their dispatch channel. Our local dispatch center does this, but only basic "alert" tones, not pagers. These audio tones are playable by op25 because they are encoded as voice, whereas pager alerts would have to be encoded as 'tones' in order to ensure accurate decoding by the receiving device.
Graham
I don't see how anything in your replies is helpful.
- They are definitely tone frames. Tones run through the vocoder are irrelevant and OP25 would handle them just fine anyway.
- Why should the user seek other solutions? The system is sending IMBE tone frames and any decoder thrown at it should handle it.
- And how does simulcast have anything to do with this? It doesn't.
To the OP: You need to record the raw signal (I/Q data or FM demodulated audio) so someone can analyze it. Then the decoder logic can be updated to accommodate tone frames and you'll get your audible alerts.
At 04:19 PM 16-06-2018, 'William Becks' wllmbecks@gmail.com [op25-dev] wrote:
What exactly are you trying to determine about the tones?  They appear to be âAlertâ tones sent by the dispatch operator ahead of the voice message. I donât think they actually serve as a signaling function as would commonly be found in analog paging systems.Â
I believe that someone has already stated that there are only a handful of specific tones or tone combinations that are provided for in the P25 vocoder. Any other tones or tone combinations transmitted into the speech input of the vocoder quote likely will not reproduce and exact replica as the source tone(s) primarily because the vocoder is designed to encode and compress speech.
Bill, WA8WG
It’s obvious that the software vocoder in OP25 does not decode all/some tones as does the DVSI hardware solution used commercially.
For your information, the simulcast question was to query why his scanner was having difficulty with missing transmission as virtually all consumer grade scanner receivers have great difficulty with simulcast systems. If you’ve been following the thread, the users wants/desires the tones that are not being decoded/reproduced by OP25. That is why he needs to seek another solution. Maybe you have the skills to rewrite the vocoder code for o25. That would be nice!
Bill
From: op25-dev@yahoogroups.com [mailto:op25-dev@yahoogroups.com] Sent: Saturday, June 16, 2018 5:20 PM To: op25-dev@yahoogroups.com Subject: RE: [op25-dev] Re: Why can't I hear fire tones?
I don't see how anything in your replies is helpful.
- They are definitely tone frames. Tones run through the vocoder are irrelevant and OP25 would handle them just fine anyway.
- Why should the user seek other solutions? The system is sending IMBE tone frames and any decoder thrown at it should handle it.
- And how does simulcast have anything to do with this? It doesn't.
To the OP: You need to record the raw signal (I/Q data or FM demodulated audio) so someone can analyze it. Then the decoder logic can be updated to accommodate tone frames and you'll get your audible alerts.
At 04:19 PM 16-06-2018, 'William Becks' wllmbecks@gmail.com [op25-dev] wrote:
What exactly are you trying to determine about the tones?  They appear to be “Alert†tones sent by the dispatch operator ahead of the voice message. I don’t think they actually serve as a signaling function as would commonly be found in analog paging systems.Â
I believe that someone has already stated that there are only a handful of specific tones or tone combinations that are provided for in the P25 vocoder. Any other tones or tone combinations transmitted into the speech input of the vocoder quote likely will not reproduce and exact replica as the source tone(s) primarily because the vocoder is designed to encode and compress speech.
Bill, WA8WG
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'William Becks' wllmbecks＠gmail.com [op25-dev] -
Andrew Porrett wap＠ica.net [op25-dev]
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Chuck Kelsey wb2edv＠roadrunner.com [op25-dev]
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gnorbury＠bondcar.com [op25-dev]
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iain macdonnell - N6ML n6ml＠dseven.org [op25-dev]
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nokoa3116＠gmail.com [op25-dev]
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zlatiolais＠yahoo.com [op25-dev]