feature systems: JFK-CH

Each phonological segment type in any language is a static, serially-ordered unit. No temporal properties are inherent to any of the features.
Each segment is a vector (that is, an ordered list) specifying the value of each relevant feature.
Combinations of the features are used to pick out particular subgroups of segments. Thus, voiced stop segments are all the segments that are [+voice, -continuant].
The features (and segments) are invariant across speaking rates, speaker's voice, position in a sequence, voice quality, pitch range, etc.
The lexical specification of words in human memory employs these features. That is, memory does not employ any concrete, speaker- or rate-dependent features.

Each feature is defined in both articulatory and acoustic terms. The rationale is that the features are communicative signals used by both speakers and hearers. Thus, they must have both an articulatory definition and an acoustic definition. The authors discuss the acoustic theory of speech production, display spectrograms of various segment types, etc.
A single universal list of features plays a phonological role for surface contrasts only. The features are assumed to be always audible and visible. Thus only a small set of features is needed - enough to cover all the surface contrasts within any language -- only about 12 features seem to be sufficient. Thus, some phonetic variation within a feature is inevitable. Thus, the feature [+flat] can be ``implemented'' in different languages or different speakers either with lip rounding or larynx lowering or pharyngeal constriction.
The features permit only binary values: +/-, plus or minus.

Each feature is defined in exclusively articulatory terms. The features are viewed as units in a speech production system. Perception is assumed to be via analysis-by-synthesis - that is, perception leans primarily on production or generation mechanisms.
There is large universal set of phonetic features, 40 or so, ``the phonetic capabilities of man''. All possible differences in speech control that languages `have available to them' are included -- that is, the phonetic features are universal and equally available to all humans at birth. Of course, 40 or so features still permit many thousands of consonant and vowel types.
Individual languages select a small subset of these (often 10-15) for the phonological contrasts within each language - the surface or near-surface phonological contrasts. Thus the features play two roles - as (relatively) concrete specifiers of universal phonetic control units, and as abstract contrast units for particular languages.
When used phonologically, the features permit only binary values, +/-. But when considered universally and phonetically, they are also normally binary, but may have, in principle, many possible values between 0 and 1.