Audio mute for digital cordless telephone
First Claim
1. A method of muting an ADPCM digital telephone signal comprising the steps of:
- detecting a data quality signal indicating data quality has transitioned from good to poor;
applying a first attenuation level of a first fixed value to a decoded form of the received signal upon initial detection of each and every transition from good to poor in said data quality signal, said first fixed value being selected to maintain intelligibility of the received signal while reducing the volume thereof, said first fixed value being applied to said decoded form of said received signal for as long as said data quality signal indicates that data quality is poor;
detecting a transition in said data quality signal from poor to good; and
responding to the detection of a transition in said data quality signal from poor to good by decreasing the attenuation level applied to the decoded form of the received signal to at least a second fixed value and continuing to attenuate the decoded form of the received signal over a period of time selected to account for the known error propagation time of the ADPCM signal.
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Accused Products
Abstract
A signal indicating the quality of the received digital data in an ADPCM cordless telephone system is monitored and a transition from good to poor quality is detected. In response to this detection, a first attenuation level is applied to the received signal, the level being selected to maintain the intelligibility of the signal to the user while lowering the volume thereof. The first attenuation level is then reduced such that reduced attenuation is maintained over a time interval selected to accommodate for the known error propagation time of the ADPCM signal. An optional clipping circuit may be employed to limit the excursion of the output audio signal.
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Citations
15 Claims
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1. A method of muting an ADPCM digital telephone signal comprising the steps of:
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detecting a data quality signal indicating data quality has transitioned from good to poor; applying a first attenuation level of a first fixed value to a decoded form of the received signal upon initial detection of each and every transition from good to poor in said data quality signal, said first fixed value being selected to maintain intelligibility of the received signal while reducing the volume thereof, said first fixed value being applied to said decoded form of said received signal for as long as said data quality signal indicates that data quality is poor; detecting a transition in said data quality signal from poor to good; and responding to the detection of a transition in said data quality signal from poor to good by decreasing the attenuation level applied to the decoded form of the received signal to at least a second fixed value and continuing to attenuate the decoded form of the received signal over a period of time selected to account for the known error propagation time of the ADPCM signal. - View Dependent Claims (2, 3, 4)
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5. Digital cordless telephone circuitry providing an output audible signal to a user and comprising:
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means for providing a data quality signal indicating a transition from good to poor signal quality of a received signal and a transition back from poor signal quality to good signal quality; a decoder means for receiving a version of said received signal and providing a decoded output signal; and means for detecting a transition from good to poor in said data quality signal and, in response to each and every transition from good to poor in said data quality signal, multiplying the output signal of said decoder means by a first attenuation signal of a first fixed value selected to maintain intelligibility of the output audible signal to the user while maintaining the audio listening level thereof, said means for detecting and multiplying further being responsive to a transition in said data quality signal from poor to good to multiply said output signal by at least a second attenuation signal of a value selected to result in less attenuation of said output signal than said first value. - View Dependent Claims (6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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Specification