Woof!

On Tue, Apr 6, 2010 at 9:47 AM, <[email protected]> wrote:
>  XX-7944 - only valid keys can/will stop recording

This is not a good idea.  If DTMF gets into a recording, then when it
gets played back it can echo back and be detected as if the far end
pressed a digit.

This is a lesson I learned the hard way a long time ago.  Here is the situation:

Caller left a message, pressed '4'.  As '4' wasn't the 'stop' key, the
audable DTMF tone got recorded into the message.

The user called into to retrieve messages, and played back this
caller's message.  The '4' DTMF digit was played (as it was happily
recorded).  It echoed back weakly (side tone, or analog hybrid, or for
whatever reason there was a small amount of echo back, like there is
in the real world).  As '4' was the 'delete' message, the echoed back
DTMF was detected and acted on.  The message deleted itself!  This was
not an isolated incident, it occurred rarely, but frequently enough to
become a real problem.  As you can imagine, it wasn't easy to figure
out what the actual problem was, as for all reasonable checks it
showed that the caller pressed 4.

Unless there is a way to suppress the DTMF audio from the recording, I
suggest that you back out this change and force any detected DTMF to
end the recording, lest you suffer the same problems going forward.

--Woof!
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