"What are the phonotactics of null phones? How many can we have between
non-null phones?" Richard WORDINGHAM, ENGLAND
"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." Piotr GASIOROWSKI, POLAND

I'd rather talk of the null phoneme. I just fail to see what a null phone
could be since all phones are recordable with machines.

Tagalog is a case in point. It has the null phoneme /Ø/, that is realized as
the glottal stop when it fills the initial phonotactic position of a
syllable (I call it the "anaclinon" in my own jargon); it has no realization
when it fills the final phonotactic position of a syllable (which I call the
e.g. /Øu 'lan/ > [?u 'lan] <ulán> "rain"; /Ø-um-u 'lan > [?u mu 'lan]
<umulán> "to rain"
/sa 'Øid/ > [sa '?id] <saíd> "consumed, exhausted"
/ba 'tuØ/ > [ba 'to] <bató> "stone"

German has the null phoneme at the initial of words apparently beginning
with a vowel.
/'Øar bait/ > [?ar bait] <Arbeit> "work"

I think it is the same in English, but I once had a discussion with native
speakers of English, and although they used it in their refutal, they
asserted they was no glottal stop at the initial of art, ease, own, out,
urge etc.

In Arabic if a word begins with a vowel, it is automatically provided with
an initial glottal stop.

/Øin ti haa?/ > [?in ti 'ha:?] "end"

Wasn't it the same in Greek, e.g. /'Øi sos/ > ['?i sos] "equal"