  We present the observed pulsation spectra of all known non-interacting ZZ
Ceti stars (hydrogen atmosphere white dwarf variables; DAVs) and examine
changes in their pulsation properties across the instability strip. We confirm
the well established trend of increasing pulsation period with decreasing
effective temperature across the ZZ Ceti instability strip. We do not find a
dramatic order of magnitude increase in the number of observed independent
modes in ZZ Ceti stars, traversing from the hot to the cool edge of the
instability strip; we find that the cool DAVs have one more mode on average
compared to the hot DAVs. We confirm the initial increase in pulsation
amplitude at the blue edge, and find strong evidence of a decline in amplitude
prior to the red edge. We present the first observational evidence that ZZ Ceti
stars lose pulsation energy just before pulsations shut down at the empirical
red edge of the instability strip.
