1980-07-23
1982-11-16
Popek, Joseph A.
179 1HF, H04M 900
Patent
active
043596061
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a voice switching control for use in a bidirectional voice-communication system including loudspeaker type telephone instruments or interphone instruments or the like, and more particularly to a control system for controlling audio signals on voice transmission lines between such instruments.
BACKGROUND ART
As is known in the art, a loudspeaker type telephone instrument has a microphone for transmitting voice signals and a loudspeaker for receiving voice signals transmitted from the microphone of another loudspeaker type telephone instrument.
The loudspeaker is capable of emitting a relatively large amount of sound energy, much more than the amount of sound energy emitted by an earphone of a conventional handheld telephone instrument. The loudspeaker and the microphone of a loudspeaker or hand-free type of telephone instrument are assembled in a relatively close relationship within the same casing or cabinet of the instrument. Inevitably, the loudspeaker is acoustically coupled with the microphone in a strong manner. An interphone instrument also has a pair of electric/acoustic and acoustic/electric converters which are acoustically coupled with each other.
The acoustic coupling between a pair of converters (loudspeaker and microphone) of a hand-free telephone instrument and/or interphone apparatus is apt to produce a number of adverse effects on the bidirectional voice-communication system with a pair of hand-free telephone or interphone instruments.
For example, assuming that a first microphone of a first hand-free telephone instrument is connected via a voice transmission line or channel to a second loudspeaker of second hand-free telephone instrument and that a second microphone of the second telephone instrument is connected via another voice transmission line to a first loudspeaker of the first telephone instrument, an acoustic energy inputted to the first microphone is fed back to itself, because a closed loop is formed owing to the acoustic coupling between the loudspeaker and the corresponding microphone. The level of the fed-back signal often becomes high enough to produce a howling.
With a view that a relatively strong acoustic coupling between the loudspeaker and the microphone is inevitable, one and probably the only technique to completely eliminate the occurrence of howling is to provide control means for disconnecting or substantially disconnecting one or more voice transmission channels so that no closed loop is formed during operation, thus making a selected voice transmission channel which is required to transmit a voice message.
Such a control means or system is called "voice switching control system" which is the subject matter of the present invention.
A typical prior voice switching control system includes a pair of voice switches or variolossers. One of the voice switches is disposed in a first voice transmission line or channel between a first microphone of the first telephone or interphone instrument or station and a second loudspeaker of the second station. The other of the voice switches is disposed in a second voice transmission line between a second microphone of the second station and a first loudspeaker of the first station. In operation, a pair of voice transmission lines is energized in a complementary manner by the switching of the two voice switches which introduces two different attenuation (loss) factors in voice signals from associated microphones. The operation mode ("ON or OFF state") of the voice switches is controlled by a control circuit which monitors a pair of outputs from the first and second microphones, i.e.--the voice signal conditions in the first and second voice transmission lines ahead of the voice switches. The two outputs are passed through wave shaping circuits to be compared by a comparator. Whenever the level of the first microphone output voice signal in the first voice transmission line is greater than the level of the second microphone output voice signal in the second voice transmissio
REFERENCES:
patent: 3755625 (1973-08-01), Maston
patent: 4139731 (1979-02-01), Hashemi et al.
"On the Study of Voice Switching Control", by J. Takahaski et al., Proceedings of Acoustic Engineering _Society of Japan, pp. 485-486, Oct. 1973.
Popek Joseph A.
TOA Electric Co., Ltd.
LandOfFree
Voice switching control system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Voice switching control system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Voice switching control system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1436899