From: etg002@email.mot.com (Tim Grothause)
Newsgroups: rec.radio.scanner
Subject: Re: CTCSS Tones
Date: 12 Nov 93 15:05:14 GMT
Organization: Motorola Land Mobile Products Sector
 
(Greg Middleton) writes:
>Are CTCSS tones the same tones that are used to activate Minitor II pagers
>are other like pagers?????
 
CTCSS is "Continuous Tone Coded Subaudible Squelch." They are frequencies 
*below* 300 Hz (cycles-per-second) that are "not heard by the radio's user 
because the frequencies used are below the typical passband of the radio's
audio circuits.(300-20,000 Hz)." In actuallity, many scanners have wide 
audio output bandwidth (read: lack the component$ to filter audio response) 
and the CTCSS tones *can* be heard as a low-frequency "hum" imposed upon the 
audio. I've seen *lots* of newbies complaing that their "reciever hums, and 
the hum is different on each channel!" ;-) CTCSS is the `generic term'; 
Manufacturers refer to their implementations as "Channel Guard", "Private 
Line", "Quite Channel", etc. CTCSS systems require a recieved signal to 
*also* have the proper subaudible tone before it will enable the audio output;
without the right tone, nothing gets put out the speaker. This allows several 
users on the same channel to *not* hear each-others conversations when each 
system uses a different tone; anyone listening with a scanner hears all traffic
.
 
*Typically* CTCSS isn't used to cause pagers to emit alert tones, BUT ("Never 
say never") *some* models of the original Minitor and the newer Minitor II 
can use CTCSS to mute the audio output. 
 
>These are the tones normally used to tone out crews.
>
>I saw a review of a new scanner and supposedly it was going to be able to
>be activated by ctcss tones?  If this is the case then I am very interested
>in it as I am a emergency responder in my county.
 
That would eliminate listening to all conversation on-channel and allow you to 
hear only the traffic associated with the CTCSS tone you specify. Nice.
 
===============================================================================
Tim Grothause, ASEE, N4GIJ, EMT-Paramedic       | etg002@email.mot.com
Sys Admin, Motorola, Applied Research Lab       | 8000 W Sunrise Blvd.
Rescue Director, Motorola Fire/Rescue Team      | Room 2128
"My opinions only, not Motorola's"              | Plantation, FL 33322
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