At 12/30/2004 09:03 AM, you wrote:
>Most DTMF pads have a chip that will do 4 rows and 4 columns.....16
>digits....
>What you need to do is mount a small switch on the case to select row 3 or
>row 4.
>from the chip output.
>When row 4 is selected, you use the row 3 keys.
>
>
>
>John VE3AMZ
Reminds me of the days when we used "column 0". This was an imaginary
column to the left of 147* that we created by switching in a capacitor on
an old telco pad in just the right place. As our DTMF decoders were 567s,
we could use any DTMF tones that we could generate.
Since ABCD was already taken for column 4, I think we resorted to using
greek characters for column 0. Autopatch code was something like
"2<alpha><gamma>*
Bob NO6B
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