When an acronym begins with a, e, f, h, i, m, n, o, r, s, x, or/ the indefinite article "an" is used. The acronym "DC" in "DC current" is used as a modifier and therefore it should be both capitalized and used as if it were an adjective to the subject noun "current". Saying "An DC current" is wrong as it can be "A or The" only. Now, you should go into discretion wars and tell me if you like my tileset so far. hehe