| 摘要 |
<p>PURPOSE:To supervise a broken line with simple constitution and to discriminate the kind of broken line by superimposing a DC component of a prescribed level onto a transmission signal, sending the result, extracting the DC component from a reception signal and discriminating the fact of broken line based on the level. CONSTITUTION:A comparator 7 discriminates the reception data from a reception signal at a receiver side 2. On the other hand, a low pass filter 8 extracts a DC component VF corresponding to a transmission offset voltage VOFS from a reception signal. If a broken transmission line 3 takes place, the DC component VF is deviated from a range between threshold levels V2 and V3 are signals L1, L2 go both to an L level. The level of the reception signal is increased to nearly twice in the open state and the DC component VF takes a value close to 2VOFS, then both the signals L1, L2 go to an H level. Then based on the signals L1, L2 as shown in figure, the control section classifies the cases into the said three patterns.</p> |
