| 摘要 |
An actuating device for use in moving a school bus safety unit, such as a stop sign or crossing arm, between a retracted position adjacent the school bus, and an extended position projecting outwardly from the bus. The actuating device includes a drive motor and a friction-type slip clutch which permits the safety unit to be manually moved from its extended or retracted positions without damage to the drive arrangement for moving the safety unit, and several alternative control circuits may be utilized to automatically or semi-automatically return the safety unit to its retracted and/or extended positions if manually moved therefrom.
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