Abstract: A gateway device includes plural electronic circuit boards with redundant structures, between first and second networks, which are different. The gateway device receives data provided through the first network and, after applying data processing, outputs data to the second network. Data processing reference timings and time information, which are common in the gateway device, are shared, the data processing is executed in synchronization with the reference timings, and synchronized packets are provided. System switching between the electronic circuit boards is executed in accordance with the time information. Thus, packet outputs are synchronously switched.

Abstract: First and second gateway devices perform TDM conversion on data from multiple packets supplied from the packet networks to generate TDM signals. A TDM exchange unit switches to the first gateway device from the second gateway device to supply the TDM network with only the TDM signal generated by the first gateway device. When the TDM exchange unit switches to the first gateway device from the second gateway device, a jitter buffer controller of the second gateway device notifies the first gateway device of the packet read order determined by the jitter buffer controller of the second gateway device, and the first gateway device determines a packet read order as the packet read order determined by the jitter buffer controller of the second gateway device.

Abstract: An echo canceler has an adaptive filter that generates an echo replica signal from a far-end signal. The filter coefficients of the adaptive filter are updated according to a residual error signal, which is obtained by subtracting the echo replica signal from a near-end signal to cancel echo. A background noise estimator estimates the near-end background noise power level from the residual error signal. A step size calculator uses the estimated near-end background noise power in determining the step size of the adaptive updating of the filter coefficients. When the estimated near-end background noise level is high, a small step size is used, which improves echo cancellation under these conditions. When the estimated near-end background noise level is low, a larger step size is used to permit rapid convergence of the filter coefficients.

Abstract: A redundancy gateway system that can avoid short interruption of data communication caused by system switching in gateway units configured in a multiplex manner for a plurality of systems, and that can maintain the communication state prior to the system switching and avoid degradation of communication quality. A duplicate of a received packet is generated, thereby supplying the packet of the same content to a configuration of gateway units. For each packet, a common write pointer corresponding to identification information appended to the packet is generated. Each gateway unit writes the packet to its own jitter buffer in accordance with the common write pointer corresponding to each supplied packet, sequentially reads out the written packet from the jitter buffer, and generates a TDM signal. One of the gateway units is selectively switched and only the TDM signal generated by the one gateway unit is supplied to a TDM network.

Abstract: A gateway device includes plural electronic circuit boards with redundant structures, between first and second networks, which are different. The gateway device receives data provided through the first network and, after applying data processing, outputs data to the second network. Data processing reference timings and time information, which are common in the gateway device, are shared, the data processing is executed in synchronization with the reference timings, and synchronized packets are provided. System switching between the electronic circuit boards is executed in accordance with the time information. Thus, packet outputs are synchronously switched.

Abstract: First and second gateway devices perform TDM conversion on data from multiple packets supplied from the packet networks to generate TDM signals. A TDM exchange unit switches to the first gateway device from the second gateway device to supply the TDM network with only the TDM signal generated by the first gateway device. When the TDM exchange unit switches to the first gateway device from the second gateway device, a jitter buffer controller of the second gateway device notifies the first gateway device of the packet read order determined by the jitter buffer controller of the second gateway device, and the first gateway device determines a packet read order as the packet read order determined by the jitter buffer controller of the second gateway device.

Abstract: A network switching apparatus which is provided between a redundancy gateway system and a packet network and enables an uninterruptible changeover in a system changeover to be performed. The apparatus includes an up-direction transfer unit and a down-direction transfer unit. The down-direction transfer unit receives a changeover notification packet accompanied with designation information of a new active system gateway apparatus which has newly been set in place of an active system gateway apparatus. After the reception of the changeover notification packet, only in the case where a down-direction packet which is newly transmitted by the packet network is accompanied with designation information of the active system gateway apparatus before the changeover, the down-direction transfer unit changes the designation information to the designation information of the new active system gateway apparatus, thereby transferring the down-direction packet to the new active system gateway apparatus.

Abstract: An echo canceler has an adaptive filter that generates an echo replica signal from a far-end signal. The filter coefficients of the adaptive filter are updated according to a residual error signal, which is obtained by subtracting the echo replica signal from a near-end signal to cancel echo. A background noise estimator estimates the near-end background noise power level from the residual error signal. A step size calculator uses the estimated near-end background noise power in determining the step size of the adaptive updating of the filter coefficients. When the estimated near-end background noise level is high, a small step size is used, which improves echo cancellation under these conditions. When the estimated near-end background noise level is low, a larger step size is used to permit rapid convergence of the filter coefficients.

Abstract: A redundancy gateway system that can avoid, to the maximum extent, short interruption of data communication caused by system switching in gateway units configured in a multiplex manner for a plurality of systems, and that can maintain the communication state prior to the system switching and avoid degradation of communication quality. A duplicate of a received packet is generated, thereby supplying the packet of the same content to a plurality of gateway units. For each packet, a common write pointer corresponding to identification information appended to the packet is generated. Each of the plurality of gateway units writes the packet to its own jitter buffer in accordance with the common write pointer corresponding to each supplied packet, sequentially reads out the written packet from the jitter buffer, and generates a TDM signal. One of the plurality of gateway units is selectively switched and only the TDM signal generated by the one gateway unit is supplied to a TDM network.

Abstract: The object of the present invention is to provide a TV system discriminator capable of being applied to when the inputted TV signal is an analog signal or a digital signal, and capable of accurately discriminating between TV systems with small differences in line number and field number. In order to achieve the above object, the TV system discriminator of the present invention comprises a separator for extracting a synchronized signal for a TV signal inputted in accordance with one of a plurality of TV systems, a phase difference sensor for sensing a phase difference of this separated synchronized signal and a prescribed reference signal, and a phase difference displacement discriminator for discriminating a TV system corresponding to an inputted TV signal based on the direction of temporal displacement of this phase difference.