Figure 1. Data terminal equipment layer model (Redrawn from the IEEE Std 802.3, 1998 Edition)
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100BaseT/1000BaseT fast link pulses
The link information is encoded in a special pulse train known as the fast link pulse (FLP) burst. The FLP builds on the LIT pulse used by 10BaseT devices as a heartbeat pulse to the link partner at the opposite end of the link. The LIT was redefined as the normal link pulse (NLP). As shown in Figure 2 , the NLP is the 10BaseT link integrity test pulse, and the FLP is a group of NLPs. Each pulse is 100 ns in width.
Figure 2. FLP and NLP comparison
By Rich Hernandez
http://www.dell.com/content/topics/global.aspx/power/en/ps1q01_hernan?c=us&cs=555&l=en&s=biz
