Abstract: An infrared transmitter is obtained that transmits a signal by changing a luminance of an infrared emitting LED, the infrared transmitter including: a transmission signal generating unit; a biasing voltage generating unit that generates a biasing voltage according to a magnitude of a transmission signal; a signal/voltage mixing unit that mixes the transmission signal and the biasing voltage; and a voltage-current conversion unit that converts a voltage into a current, in which the LED is driven by the current obtained by the conversion in the voltage-current conversion unit, so that power consumption efficiency can be improved.

Abstract: An infrared transmitter transmits a signal via an infrared ray. The infrared transmitter includes: a signal converter for converting the signal into an infrared signal; an oscillator for oscillating a carrier frequency of the infrared signal; a controller for adjusting a cutoff frequency of a filter according to the carrier frequency; and the filter provided between the oscillator and the signal converter to reduce a spurious signal of a carrier wave. The cutoff frequency of the filter is adjusted by the controller.

Abstract: It is possible to shorten a delay time from utterance to output from a speaker even in a conference audio system including an automatic mute release device. An A/D converter that converts audio signals from a plurality of microphones into digital signals, an audio level detector that detects utterance or silence depending on the level of the converted digital signal, an audio data storage unit that temporarily stores the digital signal for which the audio level detector detected utterance, a controller that controls the storage of audio data in the audio data storage unit and the reading of the audio data, and a D/A converter that converts the read audio data into analog audio signals are provided. The controller hastens read timing of the audio data in accordance with a time period of silent portion when the audio level detector detects silence in a series of the audio data.

Abstract: An infrared transmitter is obtained that transmits a signal by changing a luminance of an infrared emitting LED, the infrared transmitter including: a transmission signal generating unit; a biasing voltage generating unit that generates a biasing voltage according to a magnitude of a transmission signal; a signal/voltage mixing unit that mixes the transmission signal and the biasing voltage; and a voltage-current conversion unit that converts a voltage into a current, in which the LED is driven by the current obtained by the conversion in the voltage-current conversion unit, so that power consumption efficiency can be improved.

Abstract: An infrared transmitter transmits a signal via an infrared ray. The infrared transmitter includes: a signal converter for converting the signal into an infrared signal; an oscillator for oscillating a carrier frequency of the infrared signal; a controller for adjusting a cutoff frequency of a filter according to the carrier frequency; and the filter provided between the oscillator and the signal converter to reduce a spurious signal of a carrier wave. The cutoff frequency of the filter is adjusted by the controller.

Abstract: Even in a conference audio system having an automatic mute release device, it is possible to reduce a delay time from an utterance to output from a speaker. The system includes: an A/D converter (33) for converting an audio signal from a plurality of microphones into a digital signal; audio level detection means to detect whether the converted digital signal level indicates an utterance or no sound; audio data storage means (32) for temporarily storing the digital signal in which the audio level detection means has detected an utterance; control means (31) for controlling storage of the audio data into the audio data storage means (32) and read out of the audio data; and a D/A converter (34) for converting the read-out audio data into an analog audio signal. When the audio level detection means has detected no sound in the series of audio data, the control means (31) hastens the audio data read-out timing in correspondence to the time of the no sound portion.