[chirp_users] Fire paging (was: Baofeng UV5R dtmf on receive)///

Bear Albrecht
Sun May 26 10:34:47 PDT 2013

On 5/26/13 11:10 AM, Brad NK8J wrote:
> Most Fire Stations and ambulances require DTMF Tones to tell them which
> station is being sent out to where.
Well, not exactly.  The system here is "two-tone" which has one single 
tone transmitted for a couple of seconds and then another single tone 
for a couple of seconds.  Precise timing I can look up on Tuesday if 
needed.  Google "two tone paging" for some of the angles.  
http://www.batlabs.com/qcii.html has some of the info although it 
doesn't cover what we use, nor several other variants.

One of the tone plans out there is called "Plectron"; it's used in the 
next county to the north.  In this county we use the Motorola tone 
plan.  Here's a sample:  The first column is Motorola's "hex code" (why 
they call it that I don't know but that's what we put into the dispatch 
console to specify the tone pairs), and the other are the two tones sent 
in sequence.  (Missing initial columns are the various people's names 
and call signs.)  One annoying thing about Motorola's approach is that 
they include frequencies below 300 Hz and I have removed them whenever 
possible.  Icom and Kenwood radios can be set up to double as pagers but 
they don't work well with 296.5 and basically don't work with 288.5

3800 	553.9 	1092.4
3855 	726.8 	953.7
3801 	903.2 	1063.2
3898 	903.2 	1034.7
3803 	553.9 	304.7
3804 	553.9 	313.0
3808 	533.9 	1034.7
3818 	584.8 	1034.7
3807 	553.9 	1006.9
3815 	584.8 	953.7

DTMF is another whole thing.  It's one of many possibilities for ARES 
paging that we need to figure out.


Bear Albrecht  W5VZB
San Antonio, New Mexico

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