Abstract: Power saving techniques for radar-based proximity sensing can include conducting proximity scans with a radar system in an omnidirectional proximity sensing mode in which signals are transmitted without directionality. Once an object is detected within a threshold proximity, the radar system can then switch to a directional proximity sensing mode to provide accurate directional detection capabilities in a desired field of view (FOV).

Abstract: A signal processing method in a digital-domain includes: adding a random number sequence signal into a time-domain input signal to generate a time-domain processed input signal; performing a Fourier transform operation upon the time-domain processed input signal to generate a frequency-domain processed input signal; performing an equalizer operation upon the frequency-domain processed input signal to generate a frequency-domain output signal according to coefficients of the equalizer operation; performing an inverse Fourier transform operation upon the frequency-domain output signal to generate a time-domain output signal; generating a decision output signal and generating a time-domain error signal according to the time-domain output signal; and determining the coefficients according to the time-domain error signal and the frequency-domain processed input signal.

Abstract: A signal activity detector (SAD) receives, from a hangover addition unit of a different SAD, a final decision signal of the different SAD. The final decision signal indicates a final decision of the different SAD as to whether or not the different SAD detects activity in a received input signal. The SAD combines the final decision signal of the different SAD with a preliminary decision signal of the SAD and sends a result of the combining to a hangover addition unit of the SAD. The preliminary decision signal of the SAD indicates a preliminary decision of the SAD as to whether or not the SAD detects activity in the input signal. The hangover addition unit of the SAD generates a final decision signal of the SAD based on the result of the combining.

Abstract: At least one example embodiment discloses a method of managing a power between a host serial advanced technology attachment (SATA) interface and a device SATA interface. The method includes first requesting to enter one of power saving states, defined by a SATA protocol, and second requesting to enter a deep power saving state if one of the host SATA interface and the device SATA interface operates at the first requested power saving state. The first requesting to enter one of power saving states and the second requesting to enter a deep power saving state are performed by one of the host SATA interface and the device SATA interface.

Abstract: Method for operating a hearing device (1) that is worn by a hearing device user (2), the method comprising the steps of receiving a transmission signal (4) comprising an audio signal (4) of a sound sources (S), determining a distance (d) between the sound source (S) and the hearing device (1), and generating an output signal supplied to an output transducer (8) of the hearing device (1) by at least taking into account the audio signal (4) of the transmission signal (3) and the distance (d). Further embodiments are directed to determining an angle (?) defined by a sagittal plane (5) of the hearing device user (2) and a line drawn between the hearing device (1) and the sound source (S). The angle (?) is additionally used to generate the output signal supplied to the output transducer (8) of the hearing device (1).

Abstract: A system includes an analog front end (AFE) unit to be coupled to a power line network, and a controller coupled to the AFE unit. More specifically, the AFE unit is to receive a packet signal from the power line network wherein, based on a first gain parameter, the AFE unit is to amplify the received packet signal. The controller is configured to calculate a root-mean-square (RMS) power of the amplified packet signal. Further, the AFE unit is to calculate a second gain parameter based on the calculated RMS power of the amplified packet signal and the first gain parameter, wherein the second gain parameter is to be used to amplify the received packet signal instead of the first gain parameter.

Abstract: A method for configuring an acknowledgement for a hybrid automatic repeat request (HARQ) in a wireless communication system. The method includes receiving downlink data through one of a first downlink component carrier and a second downlink component carrier from a base station; and determining whether the first or second downlink component carrier is used for receiving the downlink data. If the first downlink component carrier is used for receiving the downlink data, the resource used for the PUCCH is determined by using a control channel element (CCE). If the second downlink component carrier is used for receiving the downlink data, the resource used for the PUCCH is determined by using a radio resource control (RRC) message. The resource used for the PUCCH is associated with an orthogonal sequence with which the ACK/NACK signal is spread.

Abstract: During audio communication between terminals, an audio quality analyzing device picks up from a network a packet containing a bit stream obtained by compression encoding of audio sent by at least one of the terminals. The device has an audio quality analyzing unit that, in addition to analyzing a header of the packet picked up, performs at least one of: an analysis of a payload header and an analysis of the bit stream contained in the payload, detects deterioration in the quality of the audio communication service, and notifies a result of the detection to an upper level device.

Abstract: Radio frequency (RF) receivers having whitened digital clocks and related methods are disclosed. Disclosed embodiments generate whitened clocks having random variations that are used to operate digital processing blocks so that interference created by the whitened clocks is seen as white noise within the received RF signal spectrum. RF input signals are received by RF front-ends (RFFEs) that output analog signals associated with channels within the RF input signals. These analog signals are converted to digital information and processed by digital receive path circuitry that outputs digital data associated with the channel. The digital receive path circuitry includes a whitened clock generator that generates a whitened clock having random variations and which a digital processing block that operates based upon the whitened clock. Further, the RFFE and the digital receive path circuitry are located within a single integrated circuit.

Abstract: A coupling device for use in a hybrid fiber coaxial (HFC) network may be configured to disable an upstream path through it when there is only noise incident on the upstream path, and enable the upstream path through it when a desired transmission from a cable modem downstream of the coupling device is incident on the upstream path. The coupling device may be a trunk amplifier, a distribution amplifier, a splitter, or the like. The coupling device may comprise a single upstream interface coupled to a plurality of downstream interfaces. The enabling and/or disabling may be in response to a signal strength indicated by the SSI being below a threshold and/or in response to one or more control messages indicating whether any downstream cable modem is, or will be, transmitting.

Abstract: An image rejection (IR) circuit is configured to receive a complex signal from a radio frequency (RF) mixer, where the complex signal includes an in-phase signal portion and a quadrature signal portion. This IR circuit may include: an in-phase path to remove first mismatch information from the in-phase signal portion and associated with at least one in-phase multi-tap filter; a quadrature path to remove second mismatch information from the quadrature signal portion and associated with at least one quadrature multi-tap filter; and a correlation unit to independently update each of the multiple taps of the in-phase multi-tap filter and the quadrature multi-tap filter according to a priority scheme.

Abstract: In a millimeter-wave radar, full-duplex operation is achieved by measuring a time interval during which a leakage signal is present in a digital baseband received signal, generating samples of the digital baseband received signal, and masking a subset of the samples corresponding to the time interval, which removes the leakage signal from the digital baseband received signal. The step of measuring the time interval may be performed during a calibration phase during which desired signals are suppressed.

Abstract: A receiver is set forth that includes a tuner circuit and a converter circuit. The tuner circuit provides an analog signal corresponding to a modulated signal that is received on a selected channel. The converter circuit includes a sample clock that is used to convert the analog signal to a digital signal at a conversion rate corresponding to the frequency of the sample clock. The sample clock is selectable between at least two different clock frequencies.

Abstract: Described is an apparatus comprising: a reference generator to provide a first reference and a second reference; a first input coupled to the first reference; a second input coupled to the second reference; and a comparator coupled to the first and second inputs, the comparator to receive a clock signal and to update an output signal according to a phase of the clock signal.

Abstract: A signal processing system and method includes a transducer for receiving an analog signal having a random component and possibly an information component. The analog signal is converted into a digital signal having sample points. A nearest-neighbor calculation component calculates the expected average nearest neighbor distance between the sample points, the actual average distance and an error value. These values are corrected for edge effects. A first randomness assessment compares the actual average distance against the expected average distance with the standard error value. A second randomness assessment compares actual repeated values in the digital signal against expected repeated values. An information processing system continues processing the signal if the assessments indicate the possibility of an information component.

Abstract: A method for detecting the digital quality of a radio signal includes: receiving a radio signal including a digital portion modulated by a series of symbols each including a plurality of samples; computing correlation points between endpoint samples in cyclic prefix regions of adjacent symbols; and using the correlation points to produce a digital signal quality metric. Receivers that implement the method are also provided.

Abstract: A configurable multimode despreader for spread spectrum applications is disclosed herein. The despreader includes a plurality of data lines, at least one selective coupler coupled to the plurality of data lines, at least one multiplier coupled to the selective coupler, and a code input line coupled to the multiplier. The selective coupler selectively couples one of the plurality of data lines with the multiplier per any one of a plurality of despreading protocols. The multiplier then multiplies a desired input data type received from the selective coupler with a despreading code chip received from the code input line to produce an observation. The programmable multimode despreader supports variable code and data modulation schemes and variable spreading factors.

Abstract: A target link signal may be received at a receiving device with the target link signal being received in a received signal also including an interfering link signal. A quality of the interfering link signal in the received signal may be estimated at the receiving device to provide an estimated interfering link signal quality. One of a plurality of interference cancellation techniques may be selected responsive to the estimated interfering link signal quality, and an interference cancellation signal may be generated using the selected one of the plurality of interference cancellation techniques. Information of the interference cancellation signal may be incorporated in the received signal. Responsive to incorporating information of the interference cancellation signal in the received signal, the received signal may be demodulated to provide a demodulated target link signal, and the demodulated target link signal may be decoded to provide a target link bit stream.

Abstract: A receiving apparatus includes: a transmission path characteristics estimating section obtaining pre-interpolation transmission path characteristic data as estimate values for transmission path characteristics as characteristics of a transmission path of an OFDM signal for transmission symbols of pilot signals by using the pilot signals contained in the OFDM signal, and filtering the pre-interpolation transmission path characteristic data by using an interpolation filter, thereby obtaining transmission path characteristic data as estimate values for transmission path characteristics for transmission symbols of the OFDM signal; a distortion correcting section performing distortion correction for the OFDM signal by using the transmission path characteristic data; and a filter controlling section controlling a pass band of the interpolation filter.

Abstract: Methods, systems and other embodiments associated with pre-processing a signal for spectral analysis are presented. A system for pre-processing a digital input signal includes a digital down converter (DDC), an interpolator, and a series of down samplers. The DDC modulates the digital input signal to create a down converted signal. The interpolator re-samples the down converted signal to produce a re-sampled signal. The series of down samplers produces down sampled signals. The multiplexer selects one of the digital input signal, the down converted signal, and the down sampled signals and routes the selected signal to an output line.

Abstract: In addition, to pilot tones which may be existent within an orthogonal frequency division multiplexing (OFDM) signal, one or more data tones within that same signal may be employed to assist with channel estimation (alternatively, detection). Once a data tone qualifies as a pseudo-pilot tone, it may be used with the pilot tones for channel estimation. A qualifier considers slicer error associated with hard decisions for a data tone to determine if it is a candidate for assistance within channel estimation. A frame within an OFDM signal may, in one situation, include no pilot tones at all, and a previously calculated channel estimate may be used to process that frame. In addition, fewer pilot tones than needed to perform accurate channel estimation (based on the channel delay spread) may be employed by using one or more pseudo-pilot tones (e.g., qualified data tones).

Abstract: The present invention discloses a method and apparatus for wide dynamic range phase conversion. In one embodiment, inphase and quadrature signal components of a complex input signal are collapsed into a single quadrant to produce a first signal representation. A scaling operation is subsequently performed on the first signal representation to produce a second signal representation. Lastly, the second signal representation is converted into the phase domain.

Abstract: A wireless communications device may include a portable housing and a temperature-compensated clock circuit carried by the portable housing. The device may further include a wireless receiver carried by the portable housing for receiving timing signals, when available, from a wireless network, and a satellite positioning clock circuit carried by the portable housing. A clock correction circuit may be carried by the portable housing for correcting the temperature-compensated clock circuit based upon timing signals from the wireless network when available, and storing historical correction values for corresponding temperatures. The clock correction circuit may also correct the temperature-compensated clock circuit based upon the stored historical correction values when timing signals are unavailable from the wireless network, and correct the satellite positioning clock based upon the temperature-compensated clock circuit.

Abstract: An apparatus according to an embodiment of the present invention for providing a reduced representation in a frequency-domain, based on a time-based RF signal, has a time-frequency converter adapted to transform the time-domain RF signal to obtain a frequency-domain representation based on the time-domain signal and an entropy encoder adapted to obtain the reduced representation based on the frequency-domain representation by entropy encoding.

Abstract: When data is disclosed to a plurality of users by using a transfer network and a transfer apparatus, data disclosure time control which cannot be adversely affected by the users is performed to reduce the difference in data disclosure time among the users. A transfer network system includes a distribution server serving as a data-distribution-source transfer apparatus, and a network terminal connected to distribution-destination user equipment. The distribution server and the network terminal each have a time keeping function and a time synchronization function for matching the time of the time keeping function with a master clock. The distribution server sends in advance disclosure data and disclosure time to the network terminal. When the time of the time keeping function of the network terminal matches the disclosure time, the network terminal sends the disclosure data to the user equipment.

Abstract: A radio frequency receiver with dual band reception and dual analog-to-digital converters (ADCs) can be configured to operate in a single channel mode or a dual channel mode to receive a single RF input channel or two RF input channels at the same or different frequency bands. In the single channel mode, the dual ADCs can be used to improve the performance of the receiver for the single input signal or the dual ADCs can be configured for reduced power consumption. In the dual channel mode, the dual ADCs operate on the individual RF input signals to realize dual band reception. In one embodiment, the receiver is configured for asymmetric dual band reception to receive a wideband input signal on a first input signal path and a narrow band input signal on a second input signal path.

Abstract: The invention relates to a digital signal generator for providing one or more phases of a local oscillator signal for use in digital to analogue converters and harmonic rejection mixers. Embodiments disclosed include a local oscillator signal generator (200) for a mixer of a radiofrequency receiver, the signal generator (200) comprising a bit sequence generator (201) having a plurality of parallel output lines (203), a digital signal generator (202) having a serial output line (204) and a plurality of input lines connected to respective output lines (203) of the bit sequence generator (201) and a clock signal input line (205), wherein the digital signal generator (202) is configured to provide an output bit sequence on the serial output line (204) at a rate given by a clock signal provided on the clock signal input line (205) and a sequence given by a sequence of bits from the bit sequence generator (201) on the plurality of input lines (203).

Abstract: In a millimeter-wave radar, full-duplex operation comprises identifying a leakage signal in a digital baseband received signal, estimating the leakage signal, synthesizing an estimated leakage signal, and subtracting the estimated leakage signal from the digital baseband received signal. The time interval during which the leakage signal occurs may be measured, and samples of the digital baseband received signal within the time interval are masked to remove the leakage.

Abstract: A system and method for improving the processing of communications signals received in the presence of narrowband interference signals. The received communications signals are time sampled and transformed into a series of spectral terms in the frequency domain that are then evaluated to identify narrowband interference signals. The identified narrowband interference terms can be calculated to a value that will optimize the corrupted spectral terms resulting from the communication, and an inverse transformation can be used to generate a time domain signal that is free from interference.

Abstract: A system provides closed-loop gain control in a WCDMA mode and open loop control in an EDGE/GSM mode. Gain control is distributed across analog devices and a digital scaler in a wireless receiver. In the WCDMA mode, a loop filter generates an error signal that is forwarded to analog and digital control paths. The analog control path includes a first adder, a programmable hysteresis element, and a lookup table. The analog control signal is responsive to thresholds, which when used in conjunction with a previous gain value determine a new gain value. The digital control path includes a second adder, a programmable delay element, and a converter. A control word is responsive to a difference of the error signal, a calibration value, and the analog control signal. Blocker detection is provided in the WCDMA mode of operation. A controller sets system parameters using a state machine.

Abstract: A method of noise filtering of a digital video sequence to reduce ghosting artifacts, the method including computing motion values for pixels in a frame of the digital video sequence based on a reference frame, computing blending factors for the pixels based on the motion values, generating filtered output pixel values by applying the blending factors to corresponding pixel values in the reference frame and the frame, wherein selected filtered output pixel values are converged toward corresponding pixel values in the frame to reduce ghosting artifacts, and outputting the filtered frame.

Abstract: An embodiment of the present invention includes a calibration system employed in a multi-input-multi-output (MIMO) system for beamforming and receiving a plurality of streams. The system includes a first calibration circuit responsive to inphase (I) and quadrature (Q) pairs of stream and operative to calibrate each I and Q pair and a second calibration circuit responsive to the calibrated I and Q pairs for all streams, wherein the first and second calibration circuits perform calibration in the time domain.

Abstract: An adjusting method for reducing local oscillation leakage or I/Q mismatch in a receiver includes the steps of: (a) detecting a current extent of local oscillation leakage or I/Q mismatch; (b) determining if an adjusting direction is correct with reference to the current extent of local oscillation leakage or I/Q mismatch thus detected, maintaining the adjusting direction if correct, and reversing the adjusting direction upon determining that the adjusting direction is incorrect; and (c) adjusting a control signal according to the adjusting direction.

Abstract: A zero-crossing gain control system is disclosed herein. The system comprises a gain control unit for amplifying an input signal to an output signal, a zero-crossing monitoring circuit for monitoring the input signal or output signal, and a register for latching the digital control signal and generating a gain control signal that controls the gain control unit. The system may further comprise a maximum write time setting circuit for generating a write signal. The digital control signal is written into the register when a zero-crossing state is monitored or a maximum write time since a change occurred on of the digital control signal is expired. An automatic gain control system is also disclosed herein and further comprises a peak detecting circuit for detecting the level of output signal, a logic circuit for lowering or restoring the digital control signal according to the result from the peak detecting circuit.

Abstract: In a multi-input multi-output communication system receiving signals transmitted through a plurality of transmission antennas by using a plurality of reception antennas, a matrix determining a position of a symbol to be detected from a received signal is calculated at a first symbol detection step, and from the subsequent step, a matrix at the current step is acquired through a simple relationship from the matrix calculated at the previous step to determine a position of a symbol to be detected.

Abstract: A communication system includes: a transmitter adapted to transmit a synchronizing clock and serial data synchronous with the synchronizing clock over a line at low amplitude; and a receiver adapted to receive the serial data and synchronizing clock from the transmitter. The receiver includes an amplifier adapted to amplify the received synchronizing clock of low amplitude to restore the clock to its original amplitude, a latched comparator adapted to latch the received serial data in synchronism with a reproduction clock, and a phase-locked circuit.

Abstract: A receiver is set forth that includes a tuner circuit and a converter circuit. The tuner circuit provides an analog signal corresponding to a modulated signal that is received on a selected channel. The converter circuit includes a sample clock that is used to convert the analog signal to a digital signal at a conversion rate corresponding to the frequency of the sample clock. The sample clock is selectable between at least two different clock frequencies.

Abstract: A radio receiver includes a first diversity antenna structure, a second diversity antenna structure, a first RF receiver section, a second RF receiver section, a combining module, and a baseband processing module. The first diversity antenna structure provides the received inbound RF signals from one of the plurality of first antennas based on a first antenna selection signal to produce first received inbound RF signals. The second diversity antenna structure provides the received inbound RF signals from one of the plurality of second antennas based on a second antenna selection signal to produce second received inbound RF signals. The first and second RF receiver sections are operably coupled to convert the first and second received inbound RF signals into first and second inbound baseband signals, respectively. The combining module combines the first and second inbound baseband signals to produce inbound baseband signals.

Abstract: The invention relates to information transmission methods, in particular to the communication interfaces of electronic devices. The inventive method makes it possible to increase the communication range and reliability by improving noise protection through the compensation of a noise signal during the transmission and reading of the signal in both wires of a communication line. The inventive method involves connecting the first pole of a voltage supply source to the first wire of a two-wire transmission line via a first resistor and connecting the second pole of said voltage supply source to the second wire of the two-wire transmission line via a second resistor. Moreover, the first and second resistors have the equal resistance values, and a receiver is connected to the two-wire transmission line between a transmitter and the voltage supply source and is provided with two current sensors. A reading signal is defined as the sum of absolute values of the measured currents.

Abstract: A broadband device (105) can detect a proximate narrowband transmission (152) from a narrowband communication device (145). The narrowband transmission (152) can be in close enough proximity (155) to at least one bearer channel of the broadband device (105) to result in interference on the narrowband reception (152) when the broadband device (105) is transmitting and the narrowband communication device (145) is concurrently receiving. Responsive to the detecting, the broadband device (105) can gate a broadband transmission (142) to ensure the broadband transmission (142) does not interfere with the proximate narrowband reception (152). In absence of detecting the narrowband transmission (152), the broadband transmission (142) from the broadband device (105) would not be gated.

Abstract: In accordance with an example embodiment of the present invention, there is at least a method, apparatus, and computer program product to perform an over-provisioning of a radio resource including a periodic channel quality indicator resource in a predetermined way, and an allocating of the radio resource in such a manner that at least one of an effective system bandwidth is reduced and out-of-band emissions related to the allocated radio resource are taken into account.

Abstract: A receiver for receiving a data signal having a channel profile may include an equalizer, to which the data signal is feedable, the equalizer having a plurality of filters and a switching device coupled to the filters, a selection device, which is disposed such that it determines a first number and a second number in dependence on the channel profile, and the switching device is disposed such that it connects a number of linear filters corresponding to the first number to form a first overall filter and connects a number of linear filters corresponding to the second number to form a second overall filter.

Abstract: A radio receiver which performs iterative decoding of a received signal is provided. The radio receiver comprises: a receiving unit receiving a signal on a symbol-by-symbol basis; a demodulation unit (303) demodulating the received signal; a last symbol timing generation unit (308) generating a last symbol timing signal on the basis of the signal demodulated by the demodulation unit (303); a modulation unit (304) modulating the signal demodulated by the demodulation unit (303); and a cancellation unit (306) cancelling an interference component of the received signal using a replica signal generated on the basis of the signal modulated by the modulation unit (304). The modulation unit (304) controls the timing of rearrangement of a data sequence on the basis of the timing of the last symbol. Thus, a radio receiver in which the receiving processing time is reduced can be provided.

Abstract: A positioning system receiver that mitigates narrowband interference by dynamically choosing the mitigation technique that yields the best interference mitigation capability with the least signal degradation to maximize receiver performance parameters such as receiver sensitivity, multipath resolution, and low power.

Abstract: A device for generating a modulation signal for an RF pulse transmitter is disclosed. The device includes a detector, a video amplifier, an analog processing device, and a modulation signal generating device. The modulation signal generating device is configured to receive an information cue from the analog processing device and to output the modulation signal. The modulation signal generating device includes a digital processing device and a signal generating device. The digital processing device is configured to receive a transmission synchro signal and the information cue and to generate a first control signal and a second control signal. The signal generating device is configured to generate a variable-amplitude Gaussian-shaped signal in response to the first control signal, to generate a variable-amplitude square-shaped signal in response to the second control signal, and to generate the modulation signal according to the Gaussian-shaped signal and the square-shaped signal.

Abstract: A clock data recovery comprises a phase detector, a phase interpolator, an initial phase detector, and an initial phase decoder. The phase detector receives an incoming data stream and an interpolated clock signal and output an early/late value indicating timing relationship between the incoming data stream and the interpolated clock signal. The phase interpolator receives the early/late signal and at least one reference clock signal and generate an interpolated clock signal considering the early/late value and the at least one reference clock signal. The initial phase detector receives the incoming data stream and output a first data indicating a phase of the incoming data stream. The initial phase decoder receives data indicating a phase of the incoming data stream and select the at least one reference clock signal from a plurality of clock signals considering the data indicating a phase of the incoming data stream.

Abstract: A system and method for correlating first pulsed signals with second pulsed signals includes a first receiving unit, a second receiving unit and a correlation device. The first receiving unit is disposed to receive from a first device one or more first pulsed signals. The first device may include a plurality of pulsed radio frequency source under test signal sources. The second receiving unit is disposed to receive from a second device one or more second pulsed signals. The second device may include a local oscillator pulsed signal source. The correlation device can correlate the first pulsed signals with the second pulsed signals to align a timing characteristic of the first pulsed signals to the equivalent timing characteristic of the second pulsed signals.

Abstract: The invention relates to frequency conversion systems, in particular for use as up-converters or down-converters in radiofrequency (RF) receivers or transmitters, exemplary embodiments including a radiofrequency receiver (1000) comprising: an RF signal input (1001); a mixing module (1002) comprising a first plurality of IF amplifiers (10041-3) each connected to the RF signal input (1001) via a switch (10031-3); a multi-phase local oscillator signal generator (1300) configured to provide a switching signal to each switch (10031-3); and a summing module (1005) configured to receive output signals from each of the IF amplifiers (10041-3) and to provide a second plurality of output IF signals from a weighted sum of the IF amplifier output signals, wherein the second plurality is different to the first plurality.

Abstract: A method and apparatus provide an IP telephone or similar device with a mechanism to receive and at least briefly loop back discovery signals received from a telecommunications device such as an Ethernet switch while not permitting the loop back of data packet signals. No mechanical relays are required and the circuitry can be fully integrated on an integrated circuit using commonly available techniques, if desired.

Abstract: According to one embodiment of the present invention, it is possible to realize a signal transmitter which is capable of reducing power consumption and which can be easily designed. A differential transmitter block outputs differential output signals fixed to a predetermined logic signal to a differential receiver block and disconnects terminating resistors from a signal transmission path in an idle state. In the differential receiver block, a differential comparator outputs a logic determined by symbols of the differential output signal from the differential transmitter block, and an operating state detector detects the idle state upon detection that time successively outputting a predetermined logic by the differential comparator reaches a predetermined time, and controls switches so as to disconnect the terminating resistors from the signal transmitter in the receiving side upon detection of the idle state.