Patent
Loudspeaking telephone circuit
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TLDR
In this paper, the speech signal is used as a control signal for detecting the extent of decreasing the acoustic coupling between the loudspeaker and the microphone of the telephone set and of the coupling between transmitting and receiving circuits of an anti-sidetone circuit from an expected worst condition for which the telephone circuit has been designed.Abstract:
In the loudspeaking telephone circuit, the speech signal is used as a control signal for detecting the extent of decreasing the acoustic coupling between the loudspeaker and the microphone of the telephone set and of the coupling between the transmitting and receiving circuits of an anti-sidetone circuit from an expected worst condition for which the telephone circuit has been designed thereby automatically decreasing the value of the variable loss utilized for preventing howling by an amount corresponding to said decrease. This circuit provides satisfactory speech communication with a smaller loss inserted than a prior art voice switch thus greatly improving unnatural sound as caused by the voice switch.read more
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Speakerphone for radio and landline telephones
TL;DR: In this paper, an improved speakerphone (120 and 130 in FIG. 1) for radio and landline telephones is described, which includes a microphone (102 and 132), a speaker (104 and 134) and unique control circuitry (106 and 136).
PatentDOI
Loudspeaking telephone system
TL;DR: A loudspeaking telephone system has a voice switch circuit in which voice signals on transmission and reception speech channels are respectively detected to produce control signals, and the losses of the variable attenuators are automatically controlled in accordance with the use conditions to minimum values which can prevent the howling, transmitting blocking and receiving blocking.
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TL;DR: Apparatus and methods for automatically reducing gain in one or both acoustic feedback paths of a cordless telephone when the handset and its base unit are operating in close proximity to one another, preventing uncontrolled feedback and audible howling even before it begins.
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Noise mitigation and mode switching in communications terminals such as telephones
TL;DR: In this article, a circuit to improve noise mitigation and mode switching in telephony is proposed, where the noise-floor level is continuously estimated by comparing its stored current value to the signal level value and substituting the latter for the former if it is less than the former.
References
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Patent
Loudspeaking communication terminal apparatus and method of operation
TL;DR: In this article, the natural tendency of a user to speak more loudly in a noisy environment characterized by the presence of monotonous ambient sound is compensated for and a more constant speech signal level is presented to the transmission facility.
Patent
Speech-controlled bilateral amplifier
TL;DR: In this paper, a speech-controlled bidirectional amplifier that includes first and second transmission channels each with a control member controlled by speech signals derived at control points preceding the control member is arranged so that in the rest condition both control members provide a high signal attenuation.
Patent
Automatic voice-path switching circuit for a speaker phone telephone set
TL;DR: In this paper, a key telephone set incorporating a microphone and loudspeaker for hands-free telecommunication includes a circuit responsive to the difference between transmitted and received signal levels for switching the telephone set from transmitting to receiving mode and back again.
Patent
Loud speaking telephone set
TL;DR: In this article, a level detector detects the signal level of the receiver channel and, if the detected level exceeds a predetermined level, a voltage value is gradually fed to an analog memory unit and thereafter added to the control signal.
Patent
Amplifier arrangement for telephone instrument
Brolin U,Lindgren O +1 more
TL;DR: An amplifier arrangement for controlling the output level of an amplifier used in a two-wire line telephone system comprises an attenuation circuit, a memory circuit, an integration circuit and a test device as mentioned in this paper.