I was considering a network run outside of my home, and purchased a super-cheap "Ethernet Lightning Protector" because there was little to lose, and I wanted to understand its workings.
Below you can see the insides after I'd opened it:
The first thing I noticed was the superb manufacturing quality (ahem). As for the design, it appears to be just clamping diodes.
I was expecting TVS's, or perhaps varistors, but I want to say they're Zeners because of the typical clear-red appearance, but I wasn't sure if there were other diodes/components of that look. They have no markings on them other than the single red band in the middle.
Q1: Anyone care to say if these are for sure Zeners?
Q2: As for protection, what would this actually provide? ESD protection? Could this really be considered lightning protection?
Also I'm wondering how these diodes would help. I know Ethernet uses a differential signal... The diodes appear to have their anodes at the "shielding" of the jacks.
Q3: So this literally wouldn't do anything without shielded cable (STP)?
That being said, I've little experience with Ethernet hardware design.
Q4: It seems that "all" or most Ethernet devices use transformers, so can it be said that there is some protection already inherent?