| 摘要 |
A method for preventing a rapid increase of sound volume in a car audio is provided to prevent erroeous operation due to the rapid increase of sound volume by maintaining a current sound volume using a period of a pulse train. A sound volume control system of a car audio is comprised of a volume encoder(30) for generating a pair of pulses having a phase difference of 90 degrees, an electronic volume IC(Integrated Circuit)(20) for varying an attenuation ratio of an analog audio signal, and a microcomputer(10) for generating a control signal based on the pair of pulses. The microcomputer(10) is comprised of a CPU(Central Processing Unit)(11), a ROM(Read Only Memory)(13), a RAM(Random Access Memory)(15), an interface(17), and a bus line(19) interconnecting the CPU(11), the ROM(13), the RAM(15), and the interface(17). The CPU(11) determines whether it increases a sound volume based on the pair of pulses or not.
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