On Sun, 21 Sep 2008 15:54:26 +0100, "ian field"
put finger to keyboard and composed:

Finding a way to reduce the duty cycle might be a means to get away with a
more commonly available lower impedance speaker.

AFAICS, at 25VDC a 40 ohm speaker would draw 600mA when the transistor
switches on, regardless of duty cycle, assuming the transistor has a
high enough gain at whatever base drive the IC provides. An MPS-A20
transistor is only rated for 100mA.

- Franc Zabkar
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