NavCad Drive line 3个选项有什么区别？

NavCad Drive line 有3个选项吗以及对应使用场景分别是，Direct drive (没有齿轮箱), Standard (a conventional gearbox with one engine in and one shaft out带齿轮箱一个主机对应一套轴系), or Compound (with two engines in and one shaft out2个主机对应1套轴系).

使用时根据具体设计需要相应选择。