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[aprssig] DTMF encoding

Lynn W. Deffenbaugh (Mr) ldeffenb at homeside.to
Wed Oct 1 15:21:55 UTC 2008


I'm confused (actually, my son (KJ4DXK) brought this up) about how using 
nnnn can actually get the right letter without programming pauses into 
the stream?  For instance:

5554444337775 = KJ4ERJ or was that L4ERJ or JJJ4ERJ?

Without a display to latch on the letter and move the cursor on the 
pause, the person driving the keyboard has no clue.  Even worse (and 
this is the 'nixer, I suspect) without coding the pauses INTO THE DTMF 
STREAM, there's no way that I know of for the receiver to know what was 
actually entered.

I was actually leaning in favor of this approach until he brought this 
up.  Seems like the EchoLink folks might have something going with the 
statement that EVERY keystroke is 2 digits.

525140327351 = KJ4ERJ is deterministic at least.  You could even extend 
it to cover lower-case should anyone really want to do such a thing.

525140357654 = KJ4erj based on hitting the E key 5 times (DEFdef) and so 
forth (76=PQRpqr 54=JKLjkl)

Lynn (D) - KJ4ERJ - Adding my $0.02 for whatever it's worth.

PS.  I really have trouble with the enter and pause with my last name.  
There's at least once voice response system out in IRS (Internal Revenue 
Service, the US tax guys) that requires me to touch tone the first 5 
characters of my last name....

DEFFE = 3...33...333...333...33# - Positively painful!

jimlux wrote:
> Bear in mind when talking about multiple key presses that most devices 
> that use this have some sort of visual feedback (e.g. an alphanumeric 
> display).  I'd hate to have anything like this with no feedback.  Hence 
> directory lookup interactive voice response systems that ask you to 
> enter the name using a single digit for each letter (using the 2=ABC 
> scheme).. Hopefully that "hashes" to a unique identifier that allows the 
> lookup to work. If not, they disambiguate by asking you "do you mean A 
> (press 1) or B (press 2)"
>
>
> Jim, W6RMK
>
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