[aprssig] Re: PL 100

Gerry Creager N5JXS gerry.creager at tamu.edu
Sun Jul 18 16:50:50 EDT 2004

PL (PrivateLine [tm]) is a Motorola trademark for CTCSS, which is the 
generic tone-coded squelch method, and stands for Continuous Tone Coded 
Squelch System.  The design process was singnificant, as there were, 
originally, 32 separate subaudible tones which had no harmonic nor 
heterodyne interrelationships with any other tone in the group.  For the 
record, GE called their version "Channel Guard" and it was interoperable 
with PL and the other CTCSS versions, although some of the 2-way sales 
guys would have you believe otherwise.

It doesn't matter what you call it.  PL was both an encode and decode 
implementation of the CTCSS standard.  So was Channel Guard.  There's no 
difference between CTCSS and PL, save the proprietary nature of the name 
of PL.

gerry n5jxs

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
> tones.
> If there really is any difference, I'd sure be glad to learn it.
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Gerry Creager -- gerry.creager at tamu.edu
Network Engineering -- AATLT, Texas A&M University	
Cell: 979.229.5301 Office: 979.458.4020 FAX: 979.847.8578
Page: 979.228.0173
Office: 903A Eller Bldg, TAMU, College Station, TX 77843

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