What does CTCSS really mean?

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KD0PEZ

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Pardon for asking....

But my understanding is CTCSS means the radio has the capability to emit a tone for repeater access.

Is there more to it than this?

Because I recently sold a radio (TM261A Kenwood) on line that I used soley for repeater operation. It did have the tone board inside as all the repaters here have tones on them, and I was able to access them with this radio.

Now the buyer is trying to say it doesn't have "CTCSS" and wants a partial refund.

I emailed him back asking if he's having trouble with repeater access.

His words to me:

I have a portable HT, @ 5 watts, which receives from 50 miles my local repeater on the hour time and updates automatic with ctcss. The radio i bought does not do this?
In the ad i did post:

This radio does have the ability to work repeaters. It does have a built in CTCSS for repeater PL tones. It also has the ability to name the repeaters
Can anyone please shed some light on this?

Thanks in advance.
 

N2MWE

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CTCSS is Continuous Tone Code Sound Squelch. It is a function that allows the radio to remain silent until the proper PL tone is received from a signal. The TSU-8 is the optional CTCSS board. A lot of people confuse PL tone transmission and CTCSS.
 

WB4CS

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PL tone is the tone transmitted from radio "B" to open squelch on radio "A".
CTCSS is the PL tone received to open squelch on radio "B" transmitted from radio "A".

Example: The repeater squelch will not open unless it receives a PL tone of 100.0. The repeater also transmits that 100.0 tone on it's output. So, you cannot key up the repeater unless you transmit a PL tone of 100.0 however you can hear the repeater's response regardless if your radio is listening for that PL tone or not. If you're radio isn't trying to receive the PL tone, you're using "carrier squelch", when the carrier from the repeater drops the squelch closes.

Same example above, but your radio is set up for "tone squelch" or CTCSS. Your radio is listening for only signals that have a 100.0 PL tone. You key up your repeater that transmits that PL tone on it's output and your radio's squelch opens - then closes when the PL tone disappears. If you were to receive a distant repeater on the same frequency that was not transmitting the 100.0 tone, your radio's squelch would not open and allow you to hear that distant repeater.

According to the owners manual, the radio will transmit a PL tone to access a repeater, but will not receive a PL tone to do tone squelch on the radio (CTCSS) without the optional TSU-8 board installed.

http://www.repeater-builder.com/kenwood/pdfs/tm-261a-261ej-461a-inst-man.pdf
 
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prcguy

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Not really. PL stands for "Private Line" which was Motorola's trademark for CTCSS and they share most of the same tone frequencies as CTCSS. PL implies both encode and decode and CTCSS usually refers to encode and decode. Even though "PL" is a Motorola thing everyone seems to adopt the term for general tone squelch just like adjustable wrenches are called crescent wrenches even though its a trademark of the Crescent Tool Company.

The TM-261A comes with tone encode and you need the optional TSU-8 board to decode and make use of the receive part of the tone squelch. The buyer of the radio seems to indicate receive problems with the tone squelch but if the radio had the TSU-8 it should work. Unless its broken.

Did you test the tone decode function before selling?
prcguy



PL tone is the tone transmitted from radio "B" to open squelch on radio "A".
CTCSS is the PL tone received to open squelch on radio "B" transmitted from radio "A".

Example: The repeater squelch will not open unless it receives a PL tone of 100.0. The repeater also transmits that 100.0 tone on it's output. So, you cannot key up the repeater unless you transmit a PL tone of 100.0 however you can hear the repeater's response regardless if your radio is listening for that PL tone or not. If you're radio isn't trying to receive the PL tone, you're using "carrier squelch", when the carrier from the repeater drops the squelch closes.

Same example above, but your radio is set up for "tone squelch" or CTCSS. Your radio is listening for only signals that have a 100.0 PL tone. You key up your repeater that transmits that PL tone on it's output and your radio's squelch opens - then closes when the PL tone disappears. If you were to receive a distant repeater on the same frequency that was not transmitting the 100.0 tone, your radio's squelch would not open and allow you to hear that distant repeater.

According to the owners manual, the radio will transmit a PL tone to access a repeater, but will not receive a PL tone to do tone squelch on the radio (CTCSS) without the optional TSU-8 board installed.

http://www.repeater-builder.com/kenwood/pdfs/tm-261a-261ej-461a-inst-man.pdf
 
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wtp

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or

or the problem is that the board is not set to the right tone. so the radio is not seen

also pl is trademarked for motorola and is the same as ctcss
they are a number of tones to open a radio, if used
they are analog or digital, 38 analog and 104 digital

the only but to this could be dtmf tones (they sound like the telephone) used to access other uses for the repeater
like a command use. ie send the temperature or voltage (health) of the radio
 

N4KVE

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When that radio was made, it came with TX PL, but RX PL was an option, & you had to pay extra to buy the RX PL board. New radios now come with TX, & RX PL. So when the OP stated the radio had PL, the buyer assumed it was both TX, & RX PL. Confusion on the buyer's part, as I don't see the seller being deceptive.
 

WB4CS

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Not really. PL stands for "Private Line" which was Motorola's trademark for CTCSS and they share most of the same tone frequencies as CTCSS. PL implies both encode and decode and CTCSS usually refers to encode and decode. Even though "PL" is a Motorola thing everyone seems to adopt the term for general tone squelch just like adjustable wrenches are called crescent wrenches even though its a trademark of the Crescent Tool Company.
Totally correct, thanks for the clarification. My description follows along the same thought process that most new amateur transceivers use in the instruction manual - stating that "PL" or "Tone" is TX/no RX and "CTCSS" or "Tone Squelch" is TX/RX.

Over the years the term "PL" has become ambiguous, kind of like how here in the South, all sodas are "Coke", even if it's a Mtn. Dew.
 
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KD0PEZ

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Thanks for the fast responses. Moonboots i think you may have hit it dead on. I was not aware that this radio could be set up to only receive certain frequencies if the correct PL tone was emitted from the transmitting source. That may have been what the buyer was trying to say.
 
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DaveNF2G

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Totally correct, thanks for the clarification. My description follows along the same thought process that most new amateur transceivers use in the instruction manual - stating that "PL" or "Tone" is TX/no RX and "CTCSS" or "Tone Squelch" is TX/RX.

Over the years the term "PL" has become ambiguous, kind of like how here in the South, all sodas are "Coke", even if it's a Mtn. Dew.
What the manufacturers are saying pertains only to how functions are labeled on their radios, not to how CTCSS actually functions. It is CTCSS regardless of whether you are transmitting or receiving. The only "difference" is in whether you program your radio to encode a tone, decode a tone, or both.

CTCSS = Continuous Tone Coded Squelch System
PL = Private Line - Motorola trademark for CTCSS
Channel Guard - GE trademark for CTCSS
 

robertmac

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I sometimes wonder what they are teaching in ham classes. I would have thought this would have been included. However, I still have to stop and think when they say encode/decode. Is that the radio I am using or the repeater. Generally, when not certain I will put the tone in my radio to transmit to the repeater and not in the receive in case the repeater does not tranmit a tone.
 

zz0468

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I sometimes wonder what they are teaching in ham classes.
They teach people how to pass the test.

I would have thought this would have been included. However, I still have to stop and think when they say encode/decode. Is that the radio I am using or the repeater.
Together, they usually mean both.

Generally, when not certain I will put the tone in my radio to transmit to the repeater and not in the receive in case the repeater does not tranmit a tone.
I generally don't bother unless I KNOW the repeater is encoding a tone, AND I have a specific reason to want to hear just that transmitter.
 

LtDoc

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What it amounts to is... if the repeater requires a tone to 'turn it on' that means more than one repeater can share a frequency and not interfere too much with each other. You have to transmit that tone to turn on that repeater. That's fine.
If you don't want to hear every thing that a certain frequency has on it then you can set your receiver to not come 'on' until it receives a particular tone. That means that if there's a nother repeater on that freq and doesn't send that tone then you won't hear it. I don't know about you, but I like to hear everything that's -there-. Someone may not know the correct tone to plug in so a particular repeater may not 'hear them. If you don't use a tone activated squelch then you may hear them, you know?
Don't wanna do that, don't wanna hear anything but particular repeaters and stations? Well, then you talk those repeater operators into using CTCSS in 'both' directions. Good luck with that. Or if your listening is so selective that you don't wanna hear anyone except particular stations, then good for you, talk everyone into using CTSS in both directions. Personally, I think that's silly. Oh well, so much for personal opinion, right?
Have fun.
- 'Doc
 

methusaleh

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I think I read almost the exact same thread somewhere else today, though now I wonder if it was the buyer asking about the radio...hmm...probably on EHam or the 'Zed...perhaps I will look back for it...
 

Darth_vader

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Continuous Tone Coded Squelch System
Continuous Tone Controlled Squelch System
Continuous Tone Controlled Squelch Suppression
Coded Tone Controlled Squelch System
Continuous Tone Code Sound Squelch...

And I think there are at least 495 more permutations thereof.
 

xmo

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I have always used the term CTCSS to mean Continuous Tone Coded Squelch system. If you Google CTCSS, the first hit that comes up is that exact definition at Wikipedia.

However, the term used by the EIA/TIA in the land mobile radio standards document TIA-603-D is actually Continuous Tone Controlled Squelch System - so maybe someone should revise the Wikipedia article citing the TIA as the authoritative source.
 

AgentCOPP1

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Just to be nitpicky, N2MWE said that it's called Continuous Tone Coded Sound Squelch, but it's actually Continuous Tone Coded Squelch System. I know Darth Vader said that there's many different names for it but the correct and official one is "Squelch System." It doesn't matter that much though.

Anyway, I think a few posters have this PL/CTCSS thing wrong. "Private Line" is simply an old trademark and it does not distinguish the actual name of the tone being transmitted. In a repeater system using tone squelch, it is in fact using CTCSS because the radios are transmitting the protocol for that system. To say that a repeater is half CTCSS and half PL is wrong. PL is just another name for CTCSS and the two are the exact same thing.

OP, I wouldn't give the buyer any money back. If he's 50 miles away, antenna efficiency is going to come into play and if he's using a bad antenna, it's no wonder that he's not getting in. You can refer him to page 22 of the TM261A's manual to prove that it does have CTCSS functionality. Don't give him money just because he's ignorant with the functionality of the radio.
 

wtp

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OP

getting back to it..
if the radio is tone capable and is using the wrong one it will not work on the repeater.
so the radio and the repeater have to be on the same tone and these need to be checked out.
 

Darth_vader

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"PL is just another name for CTCSS and the two are the exact same thing."

Yeah, only the abbreviation "pee ell" is easier (and quicker) to speak/write than "si tea si ess ess", especially in NATO/ICAO phonetics.

Curiously, most of the people I've yakked at on F/GM/MURS do seem to understand that a "PL tone" is what those little digits displayed next to the channel number on their HTs represent, even though they may have no prior radio experience beyond their cell phones. But instructing one of them to select a different "CTCSS tone" more than likely elicits a "what's that?"
 
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