Use of polyphonic characters in transliteration
Yes, there are guidelines. We won't get confused in the 什 example because PRC had long contact with Russia, but we may get confused for some unfamiliar countries.

Note that this guideline is only made and followed by authors and editors in mainland China. Taiwan and Hong Kong all have their own standards due to divergence in pronounciation. Whatsmore, Hongkong-neses prefer reading and writing in Cantonese.



From the table, you can see that we use different characters for different syllables according to which language it is.