Abstract: Upon controlling a directivity based on antenna elements of antennas, a communication coverage spread is calculated at step, a communication coverage limitation value is settled based on positional information at step, and the calculated communication coverage spread and the settled communication coverage limitation value are compared with each other at step. When the calculated communication coverage spread is larger than the communication coverage limitation value, the former is controlled to become equal to or less than the latter, and when the calculated communication coverage spread is smaller than the communication coverage limitation value, the former is controlled to reach the latter or a value at least near it.

Abstract: A first radio communication unit of a stationary information device performs a radio communication to detect an approach of a mobile terminal device. An attracting unit of the stationary information device generates, when the approach of the mobile terminal device is detected, an attraction force for attracting and fixing the mobile terminal device. A second radio communication unit of the mobile terminal device performs the radio communication with the first radio communication unit. An attracted unit of the mobile terminal device is attracted to the attraction force generated by the stationary information device.

Abstract: A first radio communication unit of a stationary information device performs a radio communication to detect an approach of a mobile terminal device. An attracting unit of the stationary information device generates, when the approach of the mobile terminal device is detected, an attraction force for attracting and fixing the mobile terminal device. A second radio communication unit of the mobile terminal device performs the radio communication with the first radio communication unit. An attracted unit of the mobile terminal device is attracted to the attraction force generated by the stationary information device.

Abstract: A digital equalizer has a digital filter. The digital filter is supplied with a digital input signal which corresponds to a multiplex signal composed of a plurality of signal components that are different in amplitude or phase and have the same frequency, and effects a computational digital filtering process on the supplied digital input signal. The digital filter is connected to a feedback circuit. The feedback circuit compares an output signal from the digital filter with a predetermined reference value signal. The feedback circuit has a multiplier which multiplies the output signal from the digital filter by a coefficient signal corresponding to an error of the output signal with respect to the predetermined reference value signal. Based on an output signal from the multiplier, the feedback circuit controls the amplitude of the output signal from the digital filter so as to be constant.