Patents in grey text have expired
HIMPP CID1: Title: Hearing aids, signal supplying apparatus, system for compensating hearing deficiencies and methods, (Engebretson et al.)
US4548082
Patent family: EP0191075 EP0214527 (AT, BE, CH, DE, FR, GB, IT, NL, SE), AU579890, AU623379, CA1240029, JP2113239, IL76031
HIMPP CID2: Title: Electronic filters, hearing aids and methods, (Engebretson et al.)
US5016280
Patent family: EP0342782 (CH, DE, FR, GB, NL), AU611781, CA1326285, JP2921849, KR142423, MY103857-A
HIMPP CID3: Title: Electronic Filters, signal conversion apparatus, hearing aids and methods
US5111419
US5225836
US5357251
US5475759
Patent family: EP0339819 (CH, DE, FR, GB, NL, SE), AU621100, CA1335674, DK173760, JP3307923, JP3308243, KR138526, TWNI-43643
HIMPP CID4: Title: Adaptive noise reduction circuit for a sound reproduction system, (Engebretson et al.)
US5412735
Patent family: EP0558312 ( CH, DE, DK, FR, GB, NL), AU658476, CA2,090,297, JP3040893,KR253539
HIMPP CID5: Title: Adaptive gain and filtering circuit for a sound reproductive system, (Engebretson et al.)
US5706352,
US5724433
Patent family: EP0693249 (DE, FR, GB),EP1175125(DE), CA2160133, JP2931101