| 摘要 |
PURPOSE:To enable the localization of failure in the long distance transmission control system and the troubleshooting easily, by detecting the potential difference between the both ends of the termination resistor provided in the current loop and detecting a failure in the transmission line. CONSTITUTION:The waveform of the output data '1011001...' from the transmitter 1 is (a), and the output waveform of the transmission driver circuit 2 is (b), and if a failure such as open wire of the transmission line 11 is taken place, no current loop is constituted, no current I0 flows (C2), and no voltage difference is produced (d2) across the termination resistor 3. Further, the output of the comparator 12 is OFF, the output (e2) of the NOT gate 19 is at ''H''. In this case, the output (g2) of the one shot multivibrator 14 sets the error FF16 via the NAND gate 15 (h2) to detect the failure in the line. |
