Cantonese bopomofo

Cantonese Bopomofo, or Cantonese Phonetic Symbols is an extended set of Bopomofo characters used to transcribe Yue Chinese and, specifically, its prestige Cantonese dialect. It was first introduced in early 1930s, and then standardized in 1950. It fell into disuse along with the original Bopomofo for Mandarin Chinese in the late 1950s.

History
The first system of phonetic characters for Cantonese was introduced in "Phonetic vocabulary of Cantonese characters for instruction of literacy to the people", 1931, by Ziu Ngaating. His system became a basis for the modern one, accepted in 1950 by the Guangdong Culture and Education department. In 1932, however, a different system was published in a draft by the Commission on the Unification of Pronunciation with supplementary symbols for non-Mandarin Sinitic languages, including Cantonese.

Symbols
Bopomofo for Cantonese contains additional characters to denote its specific sounds.

Combined rhymes
The original Bopomofo was based on a two vowel model of Mandarin phonology, it contains two sets of vowel signs, one for the /a/-nucleus and another one for the /ə/ nucleus. These characters were inherited, with /a/ set used to denote long of Cantonese, and /ə/ set for short. For the rhymes not found in Mandarin, Cantonese Bopomofo implements digraphs composed of a vowel character and a final consonants character. The monographs are highlighted in bold in the following table.

Notes:

1 Final ㆿ does not occur by itself.

2 Finals ㄝㄨ, ㄝ ㄇ , ㄝ ㄆ , ㄝ ㄊ , ㄝ ㄋ only occur in colloquial readings, they were not included in the initial draft.

Tonal Marks
Tones can be left unmarked, but if necessary, you may mark them like in the table below.

Examples
Sample transcription of one of the 300 Tang Poems: