求翻译：Most older ships and some recent ones use winches in conjunction with derricks for working cargo. The derricks may be arranged for fixed outreach working or slewing derricks may be fitted. A fixed outreach system uses two derricks ,one "topped"to a position over the ship’s side and the other to a position over the hold . The picture rig. The disadvantages of the fixed outreach systems are that firstly if the outreach requires adjustment cargo work must be interrupted, and secondly the load that can be lifted is less than the safe working load of the derricks since an indirect lift is used. Moreover considerable time and man power is required to prepare a ship for cargo working.是什么意思？

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