X-SAMPA
According to Wikipedia:
The Extended Speech Assessment Methods Phonetic Alphabet () is a variant of SAMPA developed in 1995 by John C. Wells, professor of phonetics at University College London. It is designed to unify the individual-language SAMPA alphabets, and extend SAMPA to cover the entire range of characters in the 1993 version of International Phonetic Alphabet (IPA). The result is a SAMPA-inspired remapping of the IPA into 7-bit ASCII.
…But what, you may ask, is SAMPA? Wikipedia to the rescue!
SAMPA was devised as a hack to work around the inability of text encodings to represent IPA symbols. Later, as Unicode support for IPA symbols became more widespread, the necessity for a separate, computer-readable system for representing the IPA in ASCII decreased. However, X-SAMPA is still useful as the basis for an input method for true IPA.
In other words, SAMPA was trying to solve the same problem as ASCII IPA, a couple years later. (The original ASCII IPA page was created in or before 1993.) I’m not sure whether Wells just didn’t know about ASCII IPA, or whether there was some other reason for creating SAMPA.
I personally stopped using ASCII IPA a while ago, when the Unicode encodings for IPA symbols became easily findable online. It hadn’t occurred to me until now (reading the X-SAMPA Wikipedia page quoted above) that ASCII IPA could still be useful as an input method for typing IPA, given a straightforward bit of software to change from one to the other.
I’ve never used X-SAMPA (nor SAMPA)—I only heard of it for the first time sometime in the last year or so. I can’t do a detailed comparison of X-SAMPA and ASCII IPA—I don’t know the former well enough, and it’s been a long time since I’ve used the latter. But it does look to me like Wells made a lot of the same representational choices that Kirshenbaum made; most of the English consonants and vowels are represented the same way in both systems.
But there are some differences. For example, the English word trap would be written in ASCII IPA as /tr&p/ (at least in my pronunciation), but in X-SAMPA as [tr\{p].