scope:

This ETS specifies the electrical characteristics for the electrical coupling of the telephony function implemented in Terminal Equipment (TE) to hearing aids. It specifies the level and frequency response relative to the acoustic output at the earphone, and also the noise and maximum level.

This ETS applies to all apparatus that is capable of supporting telephony and can be connected to the Public Switched Telephone Network (PSTN) or Integrated Services Digital Network (ISDN), which are intended for direct application to the ear, using for example traditional handsets or operator's headsets, and which provide an electrical output port for the prime purpose of coupling electrically to a hearing aid. This ETS may also be invoked for mobile apparatus and apparatus having cordless handsets that provide the facility for electrical coupling to hearing aids.

Although handsfree and loudspeaking devices are outside the scope of this ETS, if such apparatus also supports handset telephony as a separate function, this ETS may be invoked as part of that function.