Abstract: A method for producing an acid-reactive glass powder, an acid-reactive glass powder obtained by the method, and a dental glass ionomer cement composition comprising the acid-reactive glass powder. The dental glass ionomer cement composition has good mixing property, a sufficient working time, and simultaneously can make the dental glass ionomer cement composition exhibit superior mechanical properties. More specifically, a method for producing an acid-reactive glass powder wherein an acid-reactive glass powder having a range of 2 to 10 ?m of a 50% particle size is obtainable by pulverizing a large-particle-size acid-reactive glass powder having a range of 250 to 3000 ?m of a 50% particle size in a state where a small-particle-size acid-reactive glass powder having a range of 1 to 5 ?m of a 50% particle size coexists.

Abstract: In a receiving and transmitting apparatus, a frequency of a direct digital synthesizer provided in a local oscillating circuit is controlled in order to reduce a frequency error, based on data of a frequency error detecting circuit. The direct digital synthesizer includes a digital operation circuit for inputting data designating the frequency and outputting an amplitude value of a periodic signal synchronous with a reference clock, and digital-analog converter for converting the amplitude value of the periodic signal to an analog signal.

Abstract: A frequency synthesizer having reduced spurious components for use in a receiving and transmitting apparatus. The frequency synthesizer includes a direct digital synthesizer (DDS) for generating a first signal having a first frequency determined by channel setting data. The first signal is applied to a frequency divider to generate a divided signal having a divided frequency. The divided signal is applied to a frequency converter for shifting the divided frequency by a shift frequency interval to provide a reference signal having a reference frequency. The reference signal is applied to a phase locked loop (PLL) for generating a final signal having a predetermined frequency characteristic.

Abstract: A variable divider in which a dividing number setting parameter can be set is provided in a reference oscillator. When a frequency setting parameter is selected so that a DDS will not output a spurious at a specified level or at a level higher than the specified level within an output band of an PLL in response to an output frequency from the PLL, both a conversion function setting parameter for a variable divider in the PLL and a dividing number setting parameter for a variable divider in the reference oscillator are adjusted so that the output frequency and the selected frequency setting parameter are satisfied.

Abstract: In a transmitter-receiver having a transmitting circuit and a receiving circuit, the present invention mitigates an interference between the transmitting circuit and the receiving circuit. A quartz-crystal oscillator is provided as a common reference signal source for the local oscillators and the relation among frequencies is determined so that the frequencies such as local oscillating frequencies and intermediate frequencies within the transmitter-receiver do not overlap each other. Interferences between the transmitting circuit and the receiving circuit are mitigated to prevent a characteristic deterioration, spurious radiation, etc. Thereby the transmitter-receiver may be reduced in size and weight. Further, by sharing a quartz-crystal oscillator having a high frequency stability, narrowing of bands in radio channel spacing may be readily achieved.