piclist 2001\02\26\102303a >
Thread: DTMF Tx/Rx
face BY : Dan Michaels email (remove spam text)

pang khong lin wrote:

>Is there any way to know if the signal is too weak? What is meant by
>The signal at the transformer secondary has an amplitude of around 40 mV
>peak. Is this considered fine?

Your signal level sounds like it is on the "low" side - probably
near the minimum allowable for the chip. Possibly due to an impedance

Twist refers to the fact that the row and column DTMF tones have
slightly different amplitudes.

You might do well to read up some more on background information.
I have a several good links to this. Tomi Engdahl has a lot of
circuit info. The cisco.com article is quite helpful:


- dan michaels

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