Hands-free telephone set
First Claim
1. A hands-free telephone set including a bidirectional microphone (10), a transmitting signal analog digital converter (21), an acoustic echo canceler (60), a transmitting signal digital analog converter (31), a received signal analog digital converter (22), a received signal amplifier (81), a received signal digital analog converter (32) and a loudspeaker (40), said hands-free telephone set comprising:
- transmitting signal level automatic control means (100) for controlling a level of a transmitting digital signal produced from the transmitting signal analog digital converter (21) and passed through the acoustic echo canceler (60) so that the acoustic echo canceler (60) linearly suppresses acoustic echo produced due to an acoustic coupling between the loudspeaker (40) and the bidirectional microphone (10).
1 Assignment
0 Petitions
Accused Products
Abstract
An acoustic echo canceler and a side-tone echo canceler provided in a hands-free telephone suppress an acoustic echo and a side-tone echo respectively with few error by providing automatic gain controllers and/or limiters in the hands-free telephone so that the acoustic echo canceler and the side-tone echo canceler operate in linear, and a directional characteristic of a microphone used in the hands-free telephone for reducing the acoustic echo is controlled by a microphone direction controller so that the microphone operates as an omnidirectional microphone when a level of a received signal of the hands-free telephone is less than a designated level and as a bidirectional microphone when the level exceeds the designated level, further gains of an output of the microphone increases in a low frequency range.
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Citations
14 Claims
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1. A hands-free telephone set including a bidirectional microphone (10), a transmitting signal analog digital converter (21), an acoustic echo canceler (60), a transmitting signal digital analog converter (31), a received signal analog digital converter (22), a received signal amplifier (81), a received signal digital analog converter (32) and a loudspeaker (40), said hands-free telephone set comprising:
transmitting signal level automatic control means (100) for controlling a level of a transmitting digital signal produced from the transmitting signal analog digital converter (21) and passed through the acoustic echo canceler (60) so that the acoustic echo canceler (60) linearly suppresses acoustic echo produced due to an acoustic coupling between the loudspeaker (40) and the bidirectional microphone (10). - View Dependent Claims (2, 3, 7, 9, 10, 11)
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4. A hands-free telephone set including a bidirectional microphone (10), a transmitting signal analog digital converter (21), an acoustic echo canceler (60), a transmitting signal digital analog converter (31), a hybrid circuit (50), a received signal analog digital converter (22), a side-tone echo canceler (70), a received signal amplifier (81), a received signal digital analog converter (32) and a loudspeaker (40), said hands-free telephone set comprising:
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transmitting signal level automatic control means (100) for controlling a level of a transmitting digital signal produced from the transmitting signal analog digital converter (21) and passed through the acoustic echo canceler (60) so that the acoustic echo canceler (60) linearly suppresses acoustic echo produced due to an acoustic coupling between the loudspeaker (40) and the bidirectional microphone (10); and received signal level automatic control means (200) for controlling a level of a received digital signal produced from the received signal analog digital converter (22) and passed through the side-tone echo canceler (70) so that the side-tone echo canceler (70) linearly suppresses side-tone echo produced due to impedance mismatching occurring at the hybrid circuit (50). - View Dependent Claims (5, 6, 8, 12, 13, 14)
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Specification