CTCSS and DCS Tones -- What's the difference?

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CZ

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Noticed according to my BC785D that a mall uses CTCSS on one frequency, and DCS on the other. Since I can receive both freq.'s with the CSQ mode function on, I haven't experimented with setting up the tones--hope its easier than Trunking :!: :)

Anyway, what is the difference between DCS & CTCSS? Or is there any??
 

LarrySC

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PL Tone works like a dog whistle. BUT it's low freq audio rather than high freq audio. When you blow the whistle you cant hear it but the dog can. When a mic button is pressed to talk the person on the other end cant hear the tone but his radio can. The squelch is kept closed until the correct tone tells it to send the audio to the speaker so they can hear you. DPL or digital does the same with digital data.
 

CZ

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Well I knew they're silent tones, :) but the question was: "What's the difference between them?"
I was thinking that there had to be some sort of a difference since what appears to be two types -- DCS & CTCSS -- of tones are being used for some reason.

Both freq.'s are Narrow FM mode, Voice only.
 
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N_Jay

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CZ said:
Well I knew they're silent tones, :) but the question was: "What's the difference between them?"
I was thinking that there had to be some sort of a difference since what appears to be two types -- DCS & CTCSS -- of tones are being used for some reason.

Both freq.'s are Narrow FM mode, Voice only.

CTCSS or PL or Channel Guard is a subaudible tone sent with teh transmission to open the receiver squelch. Different users on a channel have different tones (frequencies) to keep there signal out of others receivers.

DCS or DPL or Digital Chanel Guard is a system that uses a very low bit rate digital signal sent with FSK under the analog modulation.
The digital word sent by each user group is different. The receiver decodes the word and only opewn if it matches the digital word it is looking for.

They do the same thing. They do it in different ways. One is analog, and one is digital.

They are not compatable. I.E No PL code equals a DPL code.
 

INDY72

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Also some scanners are set up so if you enter a PL/DPL code for a frq, you will only hear the user using that code, and not anyone else on that freq, unless you get skip/ducting with another user on that freq with the same PL/DPL codes.
 
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N_Jay

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milf said:
Also some scanners are set up so if you enter a PL/DPL code for a frq, you will only hear the user using that code, and not anyone else on that freq, unless you get skip/ducting with another user on that freq with the same PL/DPL codes.

Not hearing other users on a frequency is teh whole purpose of PL or DPL.

What other reason would a scanner have for you to enter a code?
 

INDY72

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Information discovery maybe?? Only a few scanners have this ability,.... same question could be asked about freq counters on scanners.. WHY?? LOL And the same answer, information discovery.
 
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N_Jay

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milf said:
Information discovery maybe?? Only a few scanners have this ability,.... same question could be asked about freq counters on scanners.. WHY?? LOL And the same answer, information discovery.

I see.

Not being a scanner person, I have not played with anything newer than a BC20 (I think that was the name)\.

So it scans in Carrier squelch, but displays the PL/DPL?
 

INDY72

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Scanners that come equipped with CTCSS/DCS Decode features example the PRO-92, can be set to open or no PL/DPL tone while scanning, and upon detction of a tone, they display the one in use for the freq,... you then need to just enter the proper one once known. All you have to do is set each individual freq to PL mode and leave the setting to none,.. then once you get the tone, enter it , if you can't find a tone, then just switch to DPL and again leave it at none till one is detected. If still there is no tone then most times you can assume its CSQ, and thus just set the freq for FM mode and your good to go. As for freqs/stations that you already know the PL/DPL just set the proper one for each chan and in the GRE/Radio Shack scanners scan in closed mode and you get only the tones you set for each chan.
 

Voyager

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N_Jay said:
They are not compatable. I.E No PL code equals a DPL code.

True, however, a DPL turn off code (sent at the end of a transmission) of 134.0 Hz WILL flase a PL docoder into reading 136.5 or 131.8 Hz. If you see a burst of either of these tones on your scanner (assuming it has a decoder), it is a strong indicator that DPL is being used.

BTW, CTCSS (generic term) = Motorola PL (Private Line) = GE CG (Channel Guard) Etc.

CDCSS (generic term) = same as above with a 'D' (Digital) before it. DCS (Digital Coded Squelch) is another generic term, but not the one the industry uses.

Joe M.
 

INDY72

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AHHHHH TY for that info... Never to old to learn something new,.. will have to watch a few freqs a lil closer then lol.
 
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N_Jay

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Voyager said:
N_Jay said:
They are not compatable. I.E No PL code equals a DPL code.

True, however, a DPL turn off code (sent at the end of a transmission) of 134.0 Hz WILL flase a PL docoder into reading 136.5 or 131.8 Hz. If you see a burst of either of these tones on your scanner (assuming it has a decoder), it is a strong indicator that DPL is being used.
. . .

Actually the 134.0 "Tone" is a null DPL code. It is the digital sequence on "1010101010 . . " used to force the DPL decoder to close.
 

Voyager

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N_Jay said:
Voyager said:
N_Jay said:
They are not compatable. I.E No PL code equals a DPL code.

True, however, a DPL turn off code (sent at the end of a transmission) of 134.0 Hz WILL flase a PL docoder into reading 136.5 or 131.8 Hz. If you see a burst of either of these tones on your scanner (assuming it has a decoder), it is a strong indicator that DPL is being used.
. . .

Actually the 134.0 "Tone" is a null DPL code. It is the digital sequence on "1010101010 . . " used to force the DPL decoder to close.

That's why I called it a code, not a tone. But, it is sent at 134 Hz. In fact, the only difference is that it's a 134 Hz square wave as opposed to a 131.8 or 136.5 Hz sine wave.

Joe M.
 
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N_Jay

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Voyager said:
N_Jay said:
Voyager said:
N_Jay said:
They are not compatable. I.E No PL code equals a DPL code.

True, however, a DPL turn off code (sent at the end of a transmission) of 134.0 Hz WILL flase a PL docoder into reading 136.5 or 131.8 Hz. If you see a burst of either of these tones on your scanner (assuming it has a decoder), it is a strong indicator that DPL is being used.
. . .

Actually the 134.0 "Tone" is a null DPL code. It is the digital sequence on "1010101010 . . " used to force the DPL decoder to close.

That's why I called it a code, not a tone. But, it is sent at 134 Hz. In fact, the only difference is that it's a 134 Hz square wave as opposed to a 131.8 or 136.5 Hz sine wave.

Joe M.

Sorry, you wrote "code", I read "tone". :oops:

Hmmm 134 Hz, or 134 BPS FSK NRZ? :p
 

Voyager

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N_Jay said:
Voyager said:
N_Jay said:
Voyager said:
N_Jay said:
They are not compatable. I.E No PL code equals a DPL code.

True, however, a DPL turn off code (sent at the end of a transmission) of 134.0 Hz WILL flase a PL docoder into reading 136.5 or 131.8 Hz. If you see a burst of either of these tones on your scanner (assuming it has a decoder), it is a strong indicator that DPL is being used.
. . .

Actually the 134.0 "Tone" is a null DPL code. It is the digital sequence on "1010101010 . . " used to force the DPL decoder to close.

That's why I called it a code, not a tone. But, it is sent at 134 Hz. In fact, the only difference is that it's a 134 Hz square wave as opposed to a 131.8 or 136.5 Hz sine wave.

Joe M.

Sorry, you wrote "code", I read "tone". :oops:

Hmmm 134 Hz, or 134 BPS FSK NRZ? :p

BPS = Hz, doesn't it? :p (at least when the code is 010101010101)

Joe M.
 
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N_Jay

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Voyager said:
N_Jay said:
Voyager said:
N_Jay said:
Voyager said:
N_Jay said:
They are not compatable. I.E No PL code equals a DPL code.

True, however, a DPL turn off code (sent at the end of a transmission) of 134.0 Hz WILL flase a PL docoder into reading 136.5 or 131.8 Hz. If you see a burst of either of these tones on your scanner (assuming it has a decoder), it is a strong indicator that DPL is being used.
. . .

Actually the 134.0 "Tone" is a null DPL code. It is the digital sequence on "1010101010 . . " used to force the DPL decoder to close.

That's why I called it a code, not a tone. But, it is sent at 134 Hz. In fact, the only difference is that it's a 134 Hz square wave as opposed to a 131.8 or 136.5 Hz sine wave.

Joe M.

Sorry, you wrote "code", I read "tone". :oops:

Hmmm 134 Hz, or 134 BPS FSK NRZ? :p

BPS = Hz, doesn't it? :p (at least when the code is 010101010101)

Joe M.

True for 2 level FSK NRZ, but there are many encoding schemes.


(OK, enough with this thread before the fun stops)
 

INDY72

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This now belongs in the category of: You know youve been in tech too long when....
 
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