Abstract: A mobile communication terminal device comprises: an A/D converter 101 for converting a transmitting analog signal into a transmitting digital signal, a digital filter 109 for applying a decimation process to a first output of a multiplexer 111 to send out to an outside if the first output is an output of the A/D converter 101 and for applying an interpolation process to a second output of a multiplexer 112 if the first output is an R-ch audio digital signal whereby the first output and the second output can be processed on time-division basis, a D/A converter 104 for converting the R-ch audio digital signal which is subjected to the interpolation process by the digital filter 109 into an analog signal, and a D/A converter 103 for converting any one of an L-ch audio digital signal and a receiving digital signal which are subjected to the interpolation process by the digital filter 109 into the analog signal.

Abstract: A control circuit includes: a temperature 30; a temperature sensing section 32; a memory 36, an amplifying section 31 to which the memory and the temperature sensor are electrically connected; a first D/A converting section 38 electrically interposed between the memory and the temperature sensing section; a second D/A converting section electrically interposed between the memory and the amplifying section 31, The amplifying section 31 includes: a polarity inverting circuit 33 connected to the temperature sensor; and a variable attenuator 34, an offset adjusting circuit 100, and an amplifying circuit 35 that are connected sequentially to the polarity inverting circuit. The amplifying section 31 is connected to a sample hold circuit 41 through a displacement buffering means 101. The memory has 8 or less working control voltage setting groups.

Abstract: A crystal oscillation apparatus and a method of adjusting the same, comprising a crystal oscillating circuit, a frequency adjusting element coupled with the crystal oscillating circuit, and a control circuit for controlling voltage to be applied to the frequency adjusting element. The control circuit comprises a temperature sensor, a temperature detecting section coupled with the temperature sensor, a memory device coupled with the temperature detecting section, an amplifier to which the memory device and the temperature sensor are coupled, a first D/A converter between the memory device and temperature detection section, and a second D/A converter between the memory device and amplifier. The memory device has no more than 8 control voltage setting groups. Each of the control voltage setting groups has temperature detection data, amplitude setting data and offset voltage data.