The Phonetic Symbol Guide is a book by Geoffrey Pullum and William Ladusaw that explains the histories and uses of the symbols of various phonetic transcription conventions.
A number were adopted into Unicode 14 and 15 and have been available in SIL fonts since February 2023.
Some typewriter substitutions made by overstriking a Latin letter with a virgule require composite encoding: Similarly ⟨ꭥ̶⟩, an unused proposal to replace Americanist ⟨ꭥ̇⟩.
Several other symbols are graphic variants of Unicode characters: A couple are more distinct graphically, but without a corresponding semantic distinction: A couple of the symbols are found in Slavic sources: The following are not supported by Unicode as of version 16.
[2] Some of the symbols are idiosyncratic proposals by well-known scholars that never caught on: A couple symbols were mentioned in the 1949 Principles of the International Phonetic Association as recent suggestions for further improvement and were never adopted: The majority of the non-Unicode symbols were proposed by George Trager to improve the Bloch & Trager system of vowel transcription and other conventions of Americanist notation, but were never adopted: