What type of system this?

[bee]

In a near by county(Frankin county Al)when they say "switch over" the transmission sounds like "squelch noise". There is not any type of voice that can be heard just "squelch noise". They can switch back and forth from normal communications to the "squelch sound.

Anyone have any idea what type of system this is?

THANKS

 

[SCPD]

Just a wild guess, but probably encrypted mode. :wink:

 

[loumaag]

Whereas encryption is a possibility, it is just as possible that they are switching to digital mode.

I assume you are talking about Franklin Co., AL. If you have have a digital scanner, and have the CTCSS set for the Sheriff's channels, try putting the scanner in regular FM mode on those freq's and see. If you don't have a digital scanner, see if you can get some information from the locals in Alabama forum.

 

[n4yek]

I have always refered to it as 'spread spectrum' communications.
Pigeon Forge, Sevierville, and Gatlinburg all use this when they
don't want to be monitored.
Here is a link that desribes it:
http://www.sss-mag.com/ss.html

Also, if you use PL tones on the frequencies your scanner will not stop
when they are encoded. This is great since I don't want to hear
the static-like noise anyway.

Danny
N4YEK

 

[nd5y]

If what you are hearing sounds like white noise (the same sound as when you open the squelch) It is probably DES or similar type encryption on analog FM.

You can't hear spread spectrum on a scanner or any other NBFM receiver because it is spread out over a large bandwith and unless you are very close to it, the signal would be below the noise floor. Also I don't believe spread spectrum is allowed in the common private land mobile services bands.

 

[Voyager]

In a near by county(Frankin county Al)when they say "switch over" the transmission sounds like "squelch noise". There is not any type of voice that can be heard just "squelch noise". They can switch back and forth from normal communications to the "squelch sound.

Anyone have any idea what type of system this is?

THANKS

I have to second the DES theory. DES sounds just like open squelch.

Joe M.

 

[W4ELL]

DES encryption

I believe it is Motorola product called DVP or Digital Voice Protection. Basically sounds like shot noise that can't be squelched. Blount County/Alcoa/Maryville TN have this same encryption. They refer to it as "Private" and it can't be monitored with commercial scanners.

I have my CTCSS tone set to the unencrypted voice tone (127.3 in my area) so the scanner won't even stop when they switch over.

Before CTCSS, this was a pain in the arse because listening at a high volume level would deafen you when they switched over.

I know Pigeon Forge/Gatlinburg/Sevierville just use speech inversion where the audio sounds like Donald Duck. The speech inversion feature found in some AOR radios and other third party devices, defeat this rather easily.

 

[n4yek]

Re: DES encryption

I know Pigeon Forge/Gatlinburg/Sevierville just use speech inversion where the audio sounds like Donald Duck. The speech inversion feature found in some AOR radios and other third party devices, defeat this rather easily.

I'm sorry but this isn't correct, ONLY the sheriff uses speech inversion.
Pigeon Forge, Gatlinburg, and Sevierville the same encryption that
sounds like plain 'white noise'. Probably the same that everyone here
is trying to identify, (btw, thanks ND5Y for correcting me on the earlier
post. I didn't know spread spectrum wasn't allowed on the 400 mhz band)

Danny
N4YEK

 

[W4ELL]

I stand corrected n4yek... thanks for the info.

I don't monitor that area very much at all unless I am up there for the weekend for the Rod Run or something. I know I hear ALOT of the inversion when I do listen but with my CTSCC on, I guess I miss all the white noise (thank goodness).

 

[Voyager]

Re: DES encryption

I believe it is Motorola product called DVP or Digital Voice Protection. Basically sounds like shot noise that can't be squelched.

DES and DVP are pretty much the same thing. DES is used mostly by PS agencies (most specify DES capability for conventional encryption), and DVP is used mostly by private systems. DVP = Digital Voice Privacy. DES = Digital Encryption Standard.

Joe M.

 

[W4ELL]

Good point Joe... there is some good info on the web about this:

This site has some good info... along with WAV samples of some of the of encryption/inversion types:
http://seussbeta.tripod.com/crypt.html

This site has some explanation of the incarnations of DVP/DES:
http://www.fordyce.org/scanning/scanning_info/encrypt.html

 

[JnglMassiv]

DES and DVP are pretty much the same thing. DES is used mostly by PS agencies (most specify DES capability for conventional encryption), and DVP is used mostly by private systems. DVP = Digital Voice Privacy. DES = Digital Encryption Standard.

Actually, DVP was intended for local PS and commercial use. DES was intended to be restricted to Federal and military non-classified use.