[计] frequency division switching system

pín fēn zhì jiāo huàn jī xì tǒng ㄆㄧㄣˊ ㄈㄣ ㄓˋ ㄐㄧㄠ ㄏㄨㄢˋ ㄐㄧ ㄒㄧˋ ㄊㄨㄥˇ