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Harris / MA/COM / GE / Ericsson Forum - For general discussion of MA/COM EDACS and ProVoice systems, including equipment.

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  #41 (permalink)  
Old 04-09-2018, 9:27 PM
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Originally Posted by kb4cvn View Post
The GE Jingle was a copyrighted trademark. So, it had to go too. This prompted the change to the three 1000 Hz beep, being generic, remains to this day.
The EDACS system here has always transmitted five 4800 Hz beeps at end of transmission. Scanners look for 4800 Hz to define the end of transmission so that must be standard across the country. See https://forums.radioreference.com/1006877-post11.html for discussion of a case where pure 4800 Hz was not transmitted and how it disrupted scanner tracking.
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Old 04-10-2018, 5:18 PM
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Well then, who is "noname987"?
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Old 04-10-2018, 7:29 PM
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Well then, who is "noname987"?
I think that noname987 was made up, it's curious that that message was his 1 and only post on RR.
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Old 05-12-2018, 1:42 PM
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There's a different kind of EDACS noise that I have a question about. It happens whenever a user keys up their radio and you hear this obnoxious loud buzzing noise before they begin speaking. Here's a recording of an example:

https://www105.zippyshare.com/v/NULddM3U/file.html

This noise usually happens right at the beginning of a transmission. It's almost as though the subscriber/user has to sit there and wait for it to stop before they can begin speaking. But if the user is keyed up, how do they know the radio/repeater is only putting out this buzzing noise and not their audio yet? And what is the technical purpose for this buzzsaw noise?
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Old 05-12-2018, 1:54 PM
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That's not an "anti-scanner tone". Your scanner isn't interpreting the digital signal as digital immediately, so you're hearing the raw digital for a bit before it starts being decoded as digital audio rather than analog. Check your scanner settings to force it to interpret the signal as digital immediately, rather than assuming analog and then switching after the fact.
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Old 05-12-2018, 2:02 PM
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This is on a mostly analog EDACS system. And the user was transmitting analog on an analog talk group. This particular buzzing noise is something I've always heard on EDACS systems for many years. Yes, it's not an anti-scanner tone. I'm just wondering what causes this buzzing noise, what is the purpose of it, and do the subscriber users have to wait for it to be over to begin speaking. Sometimes the buzzing will be very long and the user seems to just give up, unkey the radio, and key up again to speak.
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Old 05-12-2018, 3:02 PM
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Originally Posted by Homeboys-Scanna View Post
This is on a mostly analog EDACS system. And the user was transmitting analog on an analog talk group. This particular buzzing noise is something I've always heard on EDACS systems for many years...
EDACS is capable of digital transmissions. AEGIS voice encryption, and MDT data, being the intended use. The buzzing sound on the recording is 9600 baud data, alternating ones and zeros. Like a test pattern.

In my previous involvement with a large EDACS system, this buzzing sound was frequently heard, sometimes in transmissions of over a minute, and usually at the end of an MDT transmission. I never heard it in the middle of a voice transmission.

So, essentially, the buzz is EDACS data mode. You might want to find out if the system is carrying any sort of data traffic. If the data is modulated in anyway with something besides alternating ones and zeros, it sounds like noise. In that case, you hear noise followed by a short period of that buzzing noise. I've also heard it send the buzz, and periodically send actual data so it sounded like the buzz turned to noise, back to buzz, back to noise a few times. That would be a valid MDT message broken up into several parts.

No one was ever able to explain to me why the system felt the need to occupy air time with essentially nothing for long periods of time, but as I recall, watching the system manager would indicate that it was a private data call.

Edit: Listening to your recording, the noise at the end of the first blast of buzzing sounds like 9600 baud data. So, I think that was a "valid" data transmission. I don't know why it would suddenly go to voice traffic, unless your recording truncates a longer period of silence between the buzz and the voice. In that case, a channel assigned for a private data call then got assigned to a voice call.
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Last edited by zz0468; 05-12-2018 at 3:16 PM..
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Old 05-12-2018, 3:09 PM
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Well, whenever I hear it, it's usually when you're trunktracking on an analog talk group and two stations are talking back and forth. The buzz usually comes right before the person speaks. Would it be unusual for a data / MDT transmission to occur on the same talk group as a voice talk group?
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Old 05-12-2018, 3:19 PM
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Originally Posted by Homeboys-Scanna View Post
Would it be unusual for a data / MDT transmission to occur on the same talk group as a voice talk group?
Not that I've ever experienced, but there could be some configurations and operational conditions that I'm just not familiar with. It doesn't happen with every transmission, does it?
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Old 05-12-2018, 3:25 PM
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No, it's only once in a great while. I've heard this same sort of thing on multiple different EDACS systems over the years.
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Old 05-12-2018, 3:37 PM
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No, it's only once in a great while. I've heard this same sort of thing on multiple different EDACS systems over the years.
Yes, so have I.

Well, I KNOW it's the 9600 baud data transmission that it's capable of. In the transmission path from the controller to the actual transmitters, there is a dedicated 9600 baud data circuit for each and every voice channel. In EDACS, each voice channel is capable of being a control channel, or carrying AEGIS or MDT data. That data is carried by the channel's dedicated data circuit. There's another circuit for each channel to carry the voice.

When the GETC key's it's associated transmitter, it's making the final decision as to whether it's a data or voice call, so I've always suspected that there's just some glitch, software bug, or "undocumented feature" within the GETC firmware that causes them to do this once in a while.

If the GETC tells the transmitter to key in data mode, but the data channel has nothing on it to actually say, the end result could just be that buzz.

Now I'm digging up long dormant brain cells that didn't fully deal with the inner workings of the EDACS system I was involved with. That system was one of my customers, not my primary responsibility.

You now know as much about "the EDACS buzz" as I do.
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