Telecommunications – Radiotelephone system – Special service
Reexamination Certificate
1999-03-15
2001-11-20
Bost, Dwayne (Department: 2681)
Telecommunications
Radiotelephone system
Special service
C455S569200, C455S553100
Reexamination Certificate
active
06321080
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to circuits and methods for an improved speech communication system, and more particularly, to a conference telephone which utilizes one transducer from the base and one transducer from the handset to complete the communication loop.
BACKGROUND OF THE INVENTION
In a conventional conference telephone or “speakerphone,” a desktop or base unit is provided which has a loudspeaker and a microphone, both of which are utilized during a conference call. Audio amplifiers are also provided to amplify the signals received from a telephone central office (that is, signals from a “far” party) to a level that is sufficient to drive the loudspeaker, and to amplify signals coupled by the microphone prior to transmission to the telephone central office (that is, signals from a “near” party). A handset having its own speaker and microphone are provided for private telephone conversations.
Because the microphone and loudspeaker in a conventional speakerphone are both mounted within the same physical enclosure and are generally proximate one another, there is a degree of acoustic coupling between the far party speech reproduced by the loudspeaker and the near party speech received at the microphone. Such coupling typically is suppressed, using an echo suppression circuit, or canceled using an echo canceling circuit. However, when the magnitude of the far party speech is great, it is difficult for the echo canceling circuit to rapidly, accurately and smoothly determine whether the audio signals constitute “near” or “far” party signals. This is particularly true during moments when both parties are speaking insofar as the far party speech may dominate the near party speech level at the microphone. As a result, even with the use of echo canceling circuitry, there can be noticeable switching or cutting out of the speech from one or both of the parties and/or a palpable reduction in the gain of the signal in an effort to reduce undesired acoustic coupling.
These problems have been recognized in the art and various approaches have been proposed. For one approach directed to continual adjustments of an echo canceling tap profile to maintain loop stability, see application Ser. No. 09/090,733, filed: Jun. 4, 1998, for SPEAKERPHONE CONTROL BASED ON ECHO CANCELER TAP PROFILE, assigned to the present assignee and hereby incorporated in its entirety by reference. The '733 patent application also provides a thorough description of the operation and circuitry of a conference telephone.
However, what still is needed in the art is an improved conference telephone which addresses these problems and improves the efficacy of conventional canceling circuits by permitting the loudspeaker and microphone to be universally positioned relative to one another.
SUMMARY OF THE INVENTION
In a broad aspect, my invention is an improved conference telephone which permits the active loudspeaker and microphone in a communication circuit to be universally positioned relative to one another.
In one form, the conference telephone of my invention includes a base having a base-mounted speaker and a base-mounted microphone, a handset having a handset-mounted speaker and a handset-mounted microphone. A control circuit responds to the selection of a conference-call mode to generate a control signal which is used by means to (1) activate either the base-mounted speaker or the base-mounted microphone, (2) activate the handset-mounted microphone if the base-mounted speaker was activated and to activate the handset-mounted speaker if the base-mounted microphone was activated, and (3) disable any microphone other than the activated microphone.
In another form, the conference telephone of my invention includes a base having a base-mounted speaker and a handset having both a handset-mounted speaker and a handset-mounted microphone. The handset-mounted microphone has at least a first sensitivity level and a second sensitivity level which is less than the first sensitivity level. A controller responds to the selection of a conference-call mode to activate the base-mounted speaker and to set the sensitivity of the handset-mounted microphone at the first sensitivity level.
My invention also concerns a method for setting a conference telephone in a conference-call mode. The method includes the steps of activating a microphone mounted on one of the base and the handset, energizing a speaker mounted on the other of the base and the handset at a level sufficient to permit a near party to hear a far party at a distance from the conference telephone, and disabling any microphone other than the activated microphone.
In another method in accordance with my invention, the conference telephone is set in a conference-call mode by enabling a near party to speak to a far party through a microphone mounted on one of the base and the handset, enabling the near party to listen to the far party through a speaker mounted on the other of the base and the handset, and disabling the microphone on the other of the base and the handset.
In further aspects of my invention, a transducer selection routine selects the optimum transducer to use at the start of a conference call. The selection is made based upon predetermined criterion, including whether the handset is in the cradle or not, test tones, and measuring signal strengths of near and far party voices through the microphones at each of the base and handset units.
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Bost Dwayne
Darby & Darby
Gelin Jean A
Lucent Technologies - Inc.
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