I recently had a similar problem finding an ic to output audio frequency
tones.  The solution I found was to use a device from MX-com part number
803A.  This device does single frequency output and also DTMF.  The
frequency output is programmable to output non standard tones.

+++++++++++++++++++++++++++++++++++++++
++      Dan Tye
++      Chief Engineer
++      Tel-Tron Technologies Corporation
++      220 Fentress Boulevard
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++      Phone: 904-255-1921    Fax: 904-258-3782
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-----Original Message-----
From: Madis Kaal [mailto:Mast@NOMAD.EE]
Sent: Tuesday, July 20, 1999 5:09 PM
To: PICLIST@MITVMA.MIT.EDU
Subject: programmable sinewave generator chip?


I am thinking about building a digitally controlled sinewave generator
and after considering the obvious brute force, lots of components
approach and after that briefly considering CD player DAC chip I decided
that there must be an easier way. Is anyone here aware of a chip that
would
allow me to tell it a frequency of a sine wave to output, in 1Hz steps
would
be nice? It sould need no precision analog components.