On Mon, 7 Jun 1999 12:12:48 -0700 David Covick <dac@WEST.NET> writes:
>Marc,
>
>All the suggestion thus far have been excellent.
>
>As another alternative, one can also use a series inductor if there is
>not a
>resonant frequency.  This will raise the sound considerably.

The ones I've seen in pagers, alarm watches, and the like have the
inductor in parallel.  This allows using a single-ended driver like a
single NPN transistor.  (Also the choice may have been influenced by the
very low supply voltage in these devices)  The frequency that is optimal
for this circuit may not be the same as the natural resonance of the
beeper.  Obviously some experiments with an adustable oscillator are
required.  Also it seems it would be necessary to drive the transistor
with less than a 50% duty cycle.


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