[aprssig] Re: PL 100

Mark Earle wa2mct at mearle.com
Sun Jul 18 16:50:16 EDT 2004

PL is (or was?) a trademark of Motorla. "Private Line"

CTCSS is the generic term, Continous Tone Coded Squelch System

The actual tones used are an EIA evolved/ developed standard, set up so 
that mechanical generators and decoders ("reeds", "vibrasponders", etc.) 
would be less likely to falsely decode on the "wrong" tone.

At 16:35 07/18/2004 -0400, KC2MMi wrote:
 >Rodney, I'm sure there must be some reason but I've never heard one given.
 >"All" the manuals refer to PL tones and CTCSS tones as is they are different
 >things. They refer to using a PL tone to get into receivers, and using a
 >CTCSS as a selective squelch tone on your own radio, so you will only hear
 >callers who are using that same tone. (i.e., "Privacy tones" in FRS radios.)
 >Funny thing is, they are the same tones, AFAIK only the context is
 >different. PL refers to using a tone when you transmit, CTCSS refers to
 >requiring others to use it to open the squelch on your radio (once you've
 >set that) but I suppose in order to confound newcomers and prevent them from
 >joining the hobby, all the manuals deal with this as is they were different
 >If there really is any difference, I'd sure be glad to learn it.
 >aprssig mailing list
 >aprssig at lists.tapr.org

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