DIGITAL SIGNAL TRANSMISSION METHOD, DIGITAL SIGNAL TRANSMISSION SYSTEM, EXTERNAL UNIT, AND AUDIO SYSTEM

摘要

PPROBLEM TO BE SOLVED: To provide an external unit and an audio system whereby the external unit 4 transmits a digital signal to a head unit by using a signal line such as an audible sound wave signal line installed in an automobile and the signal can be outputted to both of an analog input system head unit and a digital input system head unit. PSOLUTION: In the external unit 4, the digital signal is voltage-divided by resistors 55(57) and 54, and outputted to two signal lines connected to connection members 32, 33 in a balanced form. The head unit detects voltages of the two signal lines by using one remaining signal line connected to the connection member 33 as reference and amplifies the voltage difference. Further, the head unit applies the digital signal subjected to voltage division to a parallel resistive element 54 being a resistive element of a low pass filter 40 acting like a termination resistive element of the signal line. PCOPYRIGHT: (C)2004,JPO