This product is what is known as a "LAN galvanic isolator".

I recognize it because my wife is a heart surgeon who does ablations (for tachycardia and things like that) when peoples' heart beat is off.  They need all the stray electric signals isolated.

You can buy much nicer ones, that have a proper ground (for serious surges) for $31.59 on Amazon.  Or one that is the same for $13.99.

@augwest 

see my post above.  It’s a low rent surge protector.

specifially an LAN galvanic isolator.  There about $13 on Amazon.

My wife (and all doctors that hook up patients to anything computerized) use them to prevent patient shock in the event of a major catastrophic event.

No clue how that would affect, if at all, music, other than as insurance against a rare surge.

@vinylvalet 

Interestingly, the search results are all different now under that key phrase.

You can still search “Ethernet galvanic isolator” and get good results but “LAN galvanic Isolator”’ gets you to iFi products.  Their marketing guy is clearly savvy and reads internet boards.

Try “Tupavco Ethernet Surge Protector”.  It’s $31 and much nicer with an external ground wire and stronger protection.

The $13 kind are still all over the internet, but they’re at medical supply or Walmart or the like.  

Or thr back floorboard of my wife’s Land Rover.  I think she had about 50 laying there.  Each patient gets 3-4.

Yep, at Walmart:

2X RJ45 Plug Ethernet Network Surge Protector Arrester 100MHz

Two for $14.

Get now before the search terms are tinkered with!

@erik_squires 

That's an interesting idea.  I talked with my wife about what they do -- they have two things going on. 

First, is patient safety to interrupt a surge because the patient is strapped to a machine that, in turn, is tied to the LAN.  What they do there is have the grounded/gas surge protector between the monitor and the LAN.  Having a ground wire is considered part of the standard of care and mandated by the FDA.

Second is isolation of the patient from electronic noise.  (They have multiple sensors detecting very faint electrical signals from the heart.  Kind of like a super EKG.)  This has to be very precise because they do ablations (surgery on the heart to stop irregular heart rhythms) while the patient is strapped up.  For these "very local" connections they use the simple, non-grounded, isolators.  They are typically less than $10.

The iFi silencer is one of these simple sub $10 devices, marked up.