| 摘要 |
A switching system (10) including a first signal emitter (11) and a second signal emitter (13) and a detector or sensor (12) which is adapted to detect or sense the signals. If the signal emitted by the second emitter (13) is 180 degrees out of phase with the signal emitted by the first emitter (11), the signal of the first emitter (11) is effectively cancelled such that no output is provided from the detector or sensor (12).
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