| 摘要 |
A detecting electrode is mounted on the path of a thread in a sewing machine. When a cloth is sewn in the sewing machine, a bobbin thread or a needle thread moves spatially against the detecting electrode. An electric signal is obtained on the detecting electrode in response to such movement of the thread. On the other hand, a timing signal generator generates a timing signal synchronous with the vertical movement of the needle in the sewing machine. A discriminator receives the electrical signal from the detecting electrode and the timing signal from the timing signal generator. The discriminator compares the electric signal with a reference signal when it receives the timing signal and outputs a discrimination signal in accordance with the result of the comparison.
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