| 摘要 |
A grade control feeler assembly provides a pair of spaced apart control line feelers mounted on a rotational hub such that when an obstacle such as a line stake is encountered a first feeler running in contact with the line is rotated by the obstacle. This results in the rotation, as well, of the second of the feelers into contact with the line. When the obstacle has been negotiated, a spring causes the feelers to rotate to their original positions without even a momentary loss of contact between the feeler assembly and the line.
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