Telephone apparatus with howling prevention function

Details Telephone apparatus with howling prevention function Telephone apparatus with howling prevention function

1996-03-19

2002-01-15

Chiang, Jack (Department: 2742)

Telephonic communications

Echo cancellation or suppression

Reexamination Certificate

active

06339642

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a telephone apparatus with a howling preventing function.
2. Related Background Art
In case of performing a hand-free talking, when a 2-line/4-line converting circuit exists between a calling side and a communication partner, howling occurs due to a reflection of a talking signal in the 2-line/4-line converting circuit.
There is a drawback such that an apparatus is expensive when an echo canceller is used to prevent the howling.
SUMMARY OF THE INVENTION
It is an object of the invention to improve a method of preventing a howling.
It is another object of the invention to simplify a construction or control to prevent a howling.
Further another object of the invention is to provide a telephone apparatus which is connected to a communication partner via a telephone exchange and which doesn't turn on a microphone when it is judged that a howling will occur if a speaker and the microphone are turned on.
The above and other objects and features of the present invention will become apparent from the following detailed description and the appended claims with reference to the accompanying drawings.


REFERENCES:
patent: 4741018 (1988-04-01), Potratz et al.
patent: 4969181 (1990-11-01), Ito
patent: 5036532 (1991-07-01), Metroka et al.
patent: 5073928 (1991-12-01), Shimanuki
patent: 5572575 (1996-11-01), Yamamoto et al.
patent: 61-58302 (1986-03-01), None
patent: 2-177649 (1990-07-01), None
patent: 3-248697 (1991-11-01), None
patent: 63-332937 (1998-12-01), None

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