Abstract: An electric source signal supplied from a battery of a vehicle is composed of a direct current component and an alternating current component. The alternating component is classified into an alternator noise of which a frequency changes in proportional to an engine speed of the vehicle and other noises. Also, as the engine speed is heightened, a vehicle noise in the inside of the vehicle is heightened. The direct current component of the electric source signal is removed in an alternating current component passing circuit, the other noises are removed in a band pass filter, and the alternator noise is obtained. Thereafter, a frequency of the alternator noise is calculated in a microcomputer, and a volume of a sound reproduced by a speaker of an on-vehicle stereo and a tone of the sound are adjusted according to the frequency of the alternator noise. Therefore, a driver can be entertained with a music without being disturbed by the vehicle noise.

Abstract: In a shuttle dot line printer including a hammer bank shuttling back and forth at a given speed in a direction to transverse a sheet of print paper while turning around at two opposite ends, and an endless ink ribbon uni-directionally moving through a space between the hammer bank and the sheet of print paper, the ink density of the characters printed when the hammer bank is moving in the direction opposite to the ink ribbon is lowered. To prevent such occurrence, the ink ribbon is moved at a low speed lower than a regular speed when the moving direction of the hammer bank is opposite to that of the ink ribbon. On the other hand, when the moving direction of the hammer bank is same as that of the ink ribbon, the ink ribbon is moved at the regular speed after a predetermined period of time has been expired when the hammer bank turns around at one end and starts moving in the same direction as the ink ribbon.