My understanding of phrase-level Japanese pitch accent is that each "unit" initially has low pitch, followed by high pitch (LH), then a drop after the accented syllable, if there is one. As such, apart from a "reset" of the pitch, there can never be another LH contour after the initial LH, since an accent can only either cause an HL contour, or maintain an existing LL pattern.
But for larger units -- different types of phrases, or multiple phrases, what does a "unit" correspond to? When should pitch accent be 'reset'?
Also, what happens with single-syllable accented words like 蚊? Does 蚊は have accent LL, with the rest of the phrase in L as well?