February 2013
Intermediate to advanced
480 pages
13h 35m
English
Content preview from Power Over Ethernet Interoperability GuideBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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AC Disconnect and DC Disconnect
So far, we have been implicitly assuming what is called DC disconnect. This involves the PSE taking a simply voltage-current measurement to determine if there is a valid PD on the other side or not.
This manner of implementation, which really was just Ohm’s law, unfortunately ran into intellectual property (IP) battles however strange that may sound. So an alternative method came into being, one that involved injecting a low-frequency AC wave on the line. This depends on the fact that when a PD is connected to a port, the AC impedance measured on its input terminals is significantly lower than in the case of an open port (disconnected PD). AC disconnect depends on the PSE being able to “find” the capacitor on ...
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.