效率：一个激光二极管是一种单级设备，使其具有内在的效率比多级设备。
Efficiency: a laser diode is a single-stage device so it is inherently more efficient than a multistage device.
介绍印刷术的多级是一个复杂而又非常昂贵的设备。
Introduction a multistage printing press is a complicated and very expensive piece of equipment.
其中关键性的问题，在于设计先进的汇接设备和合理的组织多级会议电话网络。
The key to the topic is to design the advanced collecting equipments and to organize the suitable multistage meeting telephone network.
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