February 2013
Intermediate to advanced
480 pages
13h 35m
English
Content preview from Power Over Ethernet Interoperability Guide
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The Power Delivery Problem
We are now realizing that for every solution of PD power, we can have another possible solution, which may not get activated for various reasons but is nevertheless present and we therefore need to make sure that we stay out of that, since this second solution is usually very lossy.
In Fig. 13.6, we show that there is a very easy way to “discover” this solution. It is present even with 100-m cable. Let us take the normal IEEE-compliant case of 100 m of CAT5e. We know that we get 42.5 V at the PD side. That leaves 7.5 V across the cable. This is the cased stated in the middle row of Table 13.2 too.
FIGURE 13.6 ...
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