| 摘要 |
An apparatus for controlling the movement of a barrier is provided. The apparatus includes a governor with a preload member. The preload member provides a preload force that releasably and magnetically couples the preload member to the governor. The preload member is configured and arranged to provide a sufficient holding force to the governor in order to hold the barrier in place. The governor is configured and arranged to, upon the preload force being selectively decoupled from the preload member, allow for the downward movement of the barrier while also forming and applying an intentional braking force to the barrier to slow the downward movement of the barrier.
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