along the same lines, you can sometimes use a bridge rectifier.  i did
this once on a CB radio that the user frequently moved between vehicles
and had reverse connected before.  surprisingly it didn't drop the
output power significantly which was my main concern, and it kept him
from blowing up any more radios.

"Eisermann, Phil [Ridg/CO]" wrote:
> ------
>
> it's for reverse-polarity protection. When power and
> ground are applied correctly, the diode is reverse
> biased and not conducting.
>
> when power and ground are reversed, the diode is
> forward biased and conducts; the voltage is limited
> to one forward diode drop (varies with diode, current
> and temperature, but you usually assume 0.7V for a
> rough estimate)
---------

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