ITU P.370:1996
ITU P.370:1996 Coupling Hearing Aids To Telephone Sets Describes recommended levels and frequency characteristics for the inductive field at the telephone earphone relative to a sound level presented at the same earphone.
Table of Contents
1Scope2Normativereferences
3Definitionsandabbreviations
3.1Definitions
3.2Abbreviations
4Magneticfieldstrengtharoundtheearcapoftelephone
handsetswhichprovideforcouplingtohearingaids
4.1Introduction
4.2Magneticfieldstrengthmeasurementsandrecommended
values
4.2.1Calibrationofacousticreceivelevel
4.2.2Magneticfieldstrengthlevel
4.2.3Linearityofthemagneticfieldstrength
4.2.4Measurementoffrequencycharacteristics
4.3Probecoil
4.3.1Dimensions
4.3.2Calibrationoftheprobecoil
4.3.3Distortion
5Characteristicsoftelephonesetsthatprovideadditional
amplificationforthebenefitofhearingimpairedusers
5.1Introduction
5.2Sendingcharacteristics
5.2.1Sensitivity
5.2.2Frequencyresponse
5.3Receivingcharacteristics
5.3.1Sensitivity
5.3.2Frequencyresponse
5.3.3Restoringnormalreceiveamplification
5.4Sidetone
6Electricalcouplingoftelephonesetstohearingaids
6.1Introduction
6.2Electricalcharacteristics
6.2.1Pointofconnectioninthetelephoneset
6.2.2Electricalcharacteristicsat
interconnectionpoint
6.3Interconnectionwiththetelephoneset
6.3.1Connectortype
6.3.2Connectorposition
6.4Safetyissues
AnnexAMeasurementofanacousto-magneticadapter
generatingamagneticfield
A.1Measurementprocedures
A.2Magneticfieldrequirements
A.3Physicalproperties
AppendixIExamplesoffrequencycharacteristicsofhearing
aidscoupledtotelephones
AppendixIIBibliography