TDM is a physical layer concept, it has no regard for the nature of the information that is being multiplexed onto the output channel. 分时多工属于实体层的概念，当资料被多工处理送到输出通道，是不需要理会资料种类的。
WAN standards typically describe both physical layer delivery methods and data link layer requirements, including physical addressing, flow control, and encapsulation. 广域网路标准典型地描述实体层的传送方法和资料链结层的需求，包括实体层定址，流量控制和封装。
The freedom tone allows the ascension to be anchored in the physical. 自由音调允许提升在物理层上被锚定。
What types of intentions require immediate relaying back to the physical? 哪些类型的意想需要立即重置回物理层？
