> What are the phonotactics of null phones? How many can we have
> between non-null phones?
If phones are bundles of properties (features, elements, etc. depending
on the model) associated with strings of "skeletal positions" (temporal
slots that serve as placeholders for phonological material), a null
segment or what Miguel called a "null phone" corresponds to an empty
string of positions (i.e. does not occupy a quantum of phonological
time), and is phonologically empty (contains no material, even in the
form of "floating" features). Therefore, it plays no role in
phonotactics. It's just a notational device used for describing the
appearance or disappearance of segments.