| 摘要 |
PURPOSE: An apparatus for detecting an error of an RS-449 line is provided to make a transmitting terminal measure voltages of a plus line and a minus line transmitted to a receiving terminal to display abnormal states of each line when the voltages are not included in a regular level, and to display normal states of the lines when the voltages are included in the regular level, so as to detect whether the error is generated in the RS-449 line. CONSTITUTION: A plus line level examiner(25) connected to a plus signal line(20) examines a level of a voltage when the voltage is changed into a high state or a low state, and decides whether a normal signal is generated. A minus line level examiner(30) connected to a minus signal line(15) measures a level of a voltage, and decides whether a normal signal is generated. A reference voltage generator(35) outputs a reference voltage having four levels to the plus line level examiner(25) and the minus line level examiner(30), to measure levels of voltages applied to the plus/the minus line level examiners(25,30). The plus line level examiner(25) compares the voltage with the reference voltage in a first normal signal display unit(40). If the voltage is a normal voltage, the first normal signal display unit(40) displays the normal voltage to an exterior. The minus line level examiner(30) compares the voltage with the reference voltage in a second normal signal display unit(45). If the voltage is a normal voltage, the second normal signal display unit(45) displays the normal voltage. If abnormal voltages are not generated from the plus/the minus line level examiners(25,30), an entire normal signal display unit(50) displays that entire signals are normal.
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