1 Scope
2
Normative references
3
Definitions and abbreviations
3.1 Definitions
3.2 Abbreviations
4
Magnetic field strength around the earcap of telephone handsets which
provide for coupling to hearing aids
4.1 Introduction
4.2 Magnetic field strength measurements and recommended values
4.2.1 Calibration of acoustic receive level
4.2.2 Magnetic field strength level
4.2.3 Linearity of the magnetic field strength
4.2.4 Measurement of frequency characteristics
4.3 Probe coil
4.3.1 Dimensions
4.3.2 Calibration of the probe coil
4.3.3 Distortion
5
Characteristics of telephone sets that provide additional amplification
for the benefit of hearing impaired users
5.1 Introduction
5.2 Sending characteristics
5.2.1 Sensitivity
5.2.2
Frequency response
5.3 Receiving characteristics
5.3.1 Sensitivity
5.3.2 Frequency response
5.3.3 Restoring normal receive amplification
5.4 Sidetone
6
Electrical coupling of telephone sets to hearing aids
6.1 Introduction
6.2 Electrical characteristics
6.2.1 Point of connection in the telephone set
6.2.2 Electrical characteristics at
interconnection point
6.3 Interconnection with the telephone set
6.3.1 Connector type
6.3.2 Connector position
6.4 Safety issues
Annex A – Measurement of an acousto-magnetic adapter generating a
magnetic field
A.1 Measurement procedures
A.2 Magnetic field requirements
A.3 Physical properties
Appendix I – Examples of frequency characteristics of hearing aids
coupled to telephones
Appendix II – Bibliography