Phonak OK plus SP fully digital hearing aid has automatic reduction of feedback, designed for moderate to severe hearing loss, battery size 13, gain range 70dBHL, fitting range <120 dB, 2 channels-Digital processing, audio set-the innovation of programming digital hearing instruments, automatic reduction of non-speech sounds, access to T-coil and FM programs, hearing instrument beeps-acoustic confirmation of manual actions and end of battery life, volume control, T-coil-magnetic induction coil for use with compatible phones, 3 manual programs.