Another xtal question:  a few days ago I ordered a few crystals,
7.3728MHz, 30pF, HC49/U case.  They arrived yesterday, and much
to my surprise they each have three leads!  I've never seen a
three wire xtal before.  As yet I've not had a chance to experiment
with them ... does anyone know anything about three wire xtals?
Should the center lead be grounded like a ceramic resonator?

Thanks,
 - Nick -