23. Apparatus as in claim 20 wherein said each phone machine further includes: first means for generating an end-time distribution for each phone based on (a) the labels entering the phone machine for said each phone and (b) a start-time distribution of said each phone; and second means for evaluating the probability that a particular phone produced an input string of labels based on the generated end-time distribution of the particular phone.
20. Apparatus as in claim 18 wherein the length of the string of labels generable by each phone machine is characterized (a) as being between a minimum length and a maximum length and (b) as having a uniform length distribution wherein the probability for each length in the length distribution between the minimum and maximum length is a uniform value; the probability of label lengths less than the minimum length or greater than the maximum length being set as zero.