Telephone handset

Details Telephone handset Telephone handset

1996-05-08

1999-07-13

Chin, Wellington

Telephonic communications

Terminal

Housing or housing component

379433, 379434, 455 90, H04M 100

Patent

active

059237503

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION

The invention relates to a telephone handset of the type for use in combination with a telephone apparatus containing the electrical and electronic components necessary for the functioning of the assembly. The invention also relates to a telephone handset of the integrated type wherein the telephone handset and the associated electrical and electronic components are accommodated as a unit in one housing. The invention relates particularly to a telephone handset of the integrated type for use as portable, hand-held, cordless telephone.


BACKGROUND OF THE INVENTION

A telephone handset typically comprises an elongate housing which defines a cavity in which a first converter such as a microphone is arranged at one end for converting received acoustic signals into an electrical signal and wherein a second converter such as a loudspeaker or telephone is arranged at another end for converting received electrical signals into an audible acoustic signal. For the sake of simplicity the respective terms microphone and loudspeaker are used in the following, without the intention of limitation, to designate the said converters.
In a telephone handset of the type for use in combination with a telephone apparatus, in general only connecting wires extend from the one to the other end in the said cavity. In a telephone handset of the integrated type the electrical and electronic components necessary for functioning are also accommodated in said cavity. In the English-language professional literature both types are called a "handset".
Particularly the above mentioned portable, cordless telephone handsets with built-in transmitting and receiving facilities have in the course of time become more compact and convenient to handle in terms of size as a result of a far-reaching miniaturization and/or integration of the electrical and electronic components. The distance between the microphone and the loudspeaker has hereby become smaller, wherein comparatively more sensitive microphones are also employed for adequate reception of speech sound etc.
This has the drawback however that the microphone also more easily picks up noise and vibrations generated by the loudspeaker. As a consequence of delays in the speech transfer the person being spoken to at the remote end during a telephone conversation will hereby have relayed back to him his own delayed voice sound, which manifests itself as an intrusive echo.
It has been found that an echo of the same level becomes the more disturbing as the delay time increases. This problem will for instance occur in transmission paths running via communication satellites, but in particular also in so-called TDMA/TDD (Time Division Multiple Access/Time Division Duplex) communication systems, for instance digital cordless communications equipment operating in accordance with the DECT standard (Digital European Cordless Telecommunications).
Use is made herein of a number of speech channels arranged in time sequence (TDMA). A first half of this number of channels is used for communication in the one direction while a second half is used for communication in the other direction (TDD). This causes an additional delay compared for instance with systems having communication channels continuously available for each direction. Particularly in the case of telephone handsets for use in such systems this additional delay imposes requirements as to the maximum permissible sound and vibration transfer or cross-talk between the loudspeaker and the microphone.
Different cross-talk paths between the microphone and the loudspeaker of a telephone handset can be distinguished: an external acoustic path through the air outside the telephone handset, an internal acoustic path via the cavity in the housing of the telephone handset and a number of mechanical vibration paths, wherein the vibrations generated by the loudspeaker are transferred mechanically via the housing, via the electrical and electronic components, via the wiring etc. to the microphone. Cross-talk can also occur electri

REFERENCES:
patent: 4163875 (1979-08-01), Cogan
patent: 4319095 (1982-03-01), Cogan
patent: 4672666 (1987-06-01), Kuhfus
patent: 4675903 (1987-06-01), Gulezian et al.
patent: 4984268 (1991-01-01), Brown et al.
patent: 5081674 (1992-01-01), Wijas et al.
patent: 5201069 (1993-04-01), Barabolak
patent: 5533099 (1996-07-01), Byrne

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