Persons with complaints under Sec. Sec. 68.4 and 68.112 that are not addressed by the states pursuant to Sec. 68.414, and all other complaints regarding rules in this part pertaining to hearing aid compatibility and volume control, may bring informal complaints as described in Sec. 68.416 through Sec. 68.420. All responsible parties of terminal equipment are subject to the informal complaint provisions specified in this section. [66 FR 7587, Jan. 24, 2001]