On Tue, 23 Aug 2005 03:15:40 -0700, wrote
(in article .com):

No reason why not a piezoelectric material will both tramsmit and
receive. In fact intelligent skin is very biological. It has evolved
independently many times. Dolphins and sharks have intelligent skin.
So, presumably, did Ichtheosaurs, although skin is not in the fossil
record.


Sport SONAR pucks work that way, but they can't send and receive at the same
time.

-- Charlie Springer