Abstract: A plurality of amplifiers corresponding to a plurality of types of transmitting signals are provided to amplify the transmitting signals to a power level at which they can be transmitted by radio. The amplifiers are driven by both power and a bias. The bias is supplied to one of the amplifiers that amplifies a to-be-transmitted transmitting signal.

Abstract: A first frame is arranged on a printed circuit board to enclose a first circuit that radiates a noise. The printed circuit board also has mounted thereon a second circuit that has a need to be protected from the noise. A second frame is arranged on the printed circuit board to enclose the second circuit. The second frame is separated from one side of the first frame by a given clearance area, and the second frame has an open side facing the one side of the first frame.

Abstract: A first frame is arranged on a printed circuit board to enclose a first circuit that radiates a noise. The printed circuit board also has mounted thereon a second circuit that has a need to be protected from the noise. A second frame is arranged on the printed circuit board to enclose the second circuit. The second frame is separated from one side of the first frame by a given clearance area, and the second frame has an open side facing the one side of the first frame.

Abstract: In a line quality monitoring method of detecting a code error rate by identifying a received optical signal using different identification levels and executing bit comparison after identification, an amplitude of the signal and noise power contained in the signal are detected, and a difference between the different identification levels is controlled to be inversely proportional to the amplitude of the signal and to be proportional to the noise power of the signal. Alternatively, the amplitude of the signal is controlled to be constant and the difference between the different identification levels is controlled to be proportional to the noise power of the signal.

Abstract: A first frame is arranged on a printed circuit board mounted with a first circuit radiating a noise and a second circuit having a need to protect it from the noise to enclose the first circuit. A second frame is prepared in a state of removed one of several sides forming the second frame, which is faces the side of the first frame. The second frame is arranged on the printed circuit board to enclose the second circuit with a given clearance area with respect to one side of the first frame.

Abstract: A plurality of amplifiers corresponding to a plurality of types of transmitting signals are provided to amplify the transmitting signals to a power level at which they can be transmitted by radio. The amplifiers are driven by both power and a bias. The bias is supplied to one of the amplifiers that amplifies a to-be-transmitted transmitting signal.

Abstract: In a line quality monitoring method of detecting a code error rate by identifying a received optical signal using different identification levels and executing bit comparison after identification, an amplitude of the signal and noise power contained in the signal are detected, and a difference between the different identification levels is controlled to be inversely proportional to the amplitude of the signal and to be proportional to the noise power of the signal. Alternatively, the amplitude of the signal is controlled to be constant and the difference between the different identification levels is controlled to be proportional to the noise power of the signal.

Abstract: An optical signal is converted by a light-receiving element into a photoelectric current. The photoelectric current is converted by a preamplifier into a positive phase voltage and the opposite phase voltage. The peaks of the positive phase output and opposite phase output are sensed and held by a first and second peak sensing circuits. The median between the output of the second peak sensing circuit and the positive phase output of the preamplifier is determined by a first median output circuit. The median between the output of the first peak sensing circuit and the opposite phase output of the preamplifier is determined by a second median output circuit. A level comparison circuit compares the outputs of the first and second median output circuits and produces a signal voltage with a constant amplitude within a specific input voltage range, thereby producing a reception signal.