"The Natural Philosopher" wrote in message
...
On 02/03/2021 21:10, charles wrote:
In article , Michael Chare
wrote:
On 02/03/2021 20:29, Chris Green wrote:
Tim+ wrote:
michael adams wrote:
Me and my neighbour both get a poor mobile signal. The sound is
distorted even if rings my mobile from next door on his mobile. Quite
possibly it only happens at certain times of day but we can not be
certain, as they say. Would a decent mobile signal booster solve
this?


Depending on your network, some providers will give/sell you a device
to route calls through your own broadband via a picocell.

My sister has one as her house is in a mobile phone €�not-spot€¢ with
abysmal signal strength on all networks.

If your network doesn€˜t have such devices, change to one that has.

They're getting more and more difficult to get nowadays

Yes, Wifi calling is the new way.

and works very well.

and works *pretty* well,unless you have marginal reception when the
stupidPhone„¢ will always pick bad cellular over good wifi...

The best ones dont.

"michael adams" wrote in message
...
"Michael Chare" wrote in message
...
On 02/03/2021 20:29, Chris Green wrote:
Tim+ wrote:
michael adams wrote:
Me and my neighbour both get a poor mobile signal. The sound is
distorted
even if rings my mobile from next door on his mobile. Quite possibly
it
only happens at certain times of day but we can not be certain, as
they
say. Would a decent mobile signal booster solve this?


Depending on your network, some providers will give/sell you a device
to
route calls through your own broadband via a picocell.

My sister has one as her house is in a mobile phone €œnot-spot€� with
abysmal
signal strength on all networks.

If your network doesnt have such devices, change to one that has.

They're getting more and more difficult to get nowadays

Yes, Wifi calling is the new way.

Although we are close my phone can't pick up his wifi because the walls
insulation uses heat reflective metal foil.

It isnt his wifi it uses, its yours.

Should I use a powerline adapter to bring the signal from his router into
my house?

Nope, see above.

On 03/03/2021 15:01, The Natural Philosopher wrote:
On 03/03/2021 14:59, The Natural Philosopher wrote:
On 03/03/2021 14:51, Michael Chare wrote:
On 03/03/2021 13:10, michael adams wrote:
"Michael Chare" wrote in message
...
On 02/03/2021 20:29, Chris Green wrote:
Tim+ wrote:
michael adams wrote:
Me and my neighbour both get a poor mobile signal. The sound is
distorted
even if rings my mobile from next door on his mobile. Quite
possibly it
only happens at certain times of day but we can not be certain,
as they
say. Would a decent mobile signal booster solve this?


Depending on your network, some providers will give/sell you a
device to
route calls through your own broadband via a picocell.

My sister has one as her house is in a mobile phone €œnot-spot€�
with abysmal
signal strength on all networks.

If your network doesnt have such devices, change to one that has.

They're getting more and more difficult to get nowadays

Yes, Wifi calling is the new way.

--
Michael Chare

Although we are close my phone can't pick up his wifi because the
walls insulation uses heat reflective metal foil.

Should I use a powerline adapter to bring the signal from his router
into my house?

powerline doesn't bridge houses. It barely works on one ring main


If he is agreeable, you should run an ethrnet cable from his house to
yours. In your house you could then used an old router appropriately
configured to broadcast the Wifi signal. There are ethernet cables
that are suitable for use outside.Â* In an ideal world the device in
your house should be a Wifi access point powered by PoE from his
house to avoid any risks from the properties being connected to
different power supply electrical phases.

Ethernet uses isolation transformers on inputs and outputs so there is
no possibility of electrical LF connection via a cat 5 cable for
precisely this reason. In offices having different rooms on different
phases is commonplace. In order to render Ethernet viable in such
spaces, the spec calls for mains isolated transformer coupled IO.

https://electronics.stackexchange.co...ically-coupled



Followup. Power over Ethernet BREAKS the safety of Ethernet by
transmitting DC power over the Ethernet, It is LESS safe than having
local power


PoE is used in offices. I would expect the equipment to conform to the
same or similar standard. It would make sense for the voltage to be
provided via the an isolating transformer in the RJ45 connecting chip.


--
Michael Chare

"michael adams" wrote in message
...
Me and my neighbour both get a poor mobile signal. The sound is distorted even if rings
my mobile from next door on his mobile. Quite possibly it only happens at certain times
of day but we can not be certain, as they say. Would a decent mobile signal booster
solve this?





michael adams

...



To whom it may concern, and as a matter of record, I did not
post the above message.



michael adams

....

now posting exclusively via GigaNews

"michael adams" wrote in message
...

Although we are close my phone can't pick up his wifi because the walls insulation uses
heat reflective metal foil.

Should I use a powerline adapter to bring the signal from his router into my house?


To whom it may concern, and as a matter of record, I did not
post the above message.



michael adams

....

now posting exclusively via GigaNews

On Thu, 4 Mar 2021 05:27:55 +1100, Fred, better known as cantankerous
trolling senile geezer Rodent Speed, wrote:

FLUSH the trolling senile ****head's latest troll**** unread

--
Richard addressing senile Rodent Speed:
"**** you're thick/pathetic excuse for a troll."
MID:

"Martin Brown" wrote in message
...
On 03/03/2021 12:59, Michael Chare wrote:
On 03/03/2021 10:33, Martin Brown wrote:
On 03/03/2021 09:34, The Natural Philosopher wrote:
On 02/03/2021 21:10, charles wrote:
In article , Michael Chare
wrote:

Yes, Wifi calling is the new way.

and works very well.

and works *pretty* well,unless you have marginal reception when the
stupidPhone„¢ will always pick bad cellular over good wifi...

Put it in aeroplane mode and it will ignore cellular signals. You just
have to remember to enable it again when you go out. My home reception
is pretty marginal so for best battery life I put it into Wifi only.

It helps save power not to have it go - no signal, "ET phone home" at
maximum possible transmit power on a regular basis. My battery life app
also shows effective signal level the correlation is very striking.


That is a common suggestion, but it has never worked on my Xiaomi phone
running Android 10 with the latest update. After reading this thread I
google about this problem and found the "Wifi Calling" app which does let
me set Wifi calling as the prefered method of connection.

I think the designers of mobile phone (and TV) settings pages were fans of
Zork's "maze of twisty little passages all alike exits are N/E/S/W".

They never make it easy to find some of the more important config
settings. Defaults on TVs are typically burn your eyes out bright and
cartoon levels of colour saturation to work in a shop window display!

Does anyone actually have shop window displays of TVs anymore ?

On 03/03/2021 19:44, Michael Chare wrote:
On 03/03/2021 15:01, The Natural Philosopher wrote:
On 03/03/2021 14:59, The Natural Philosopher wrote:
On 03/03/2021 14:51, Michael Chare wrote:
On 03/03/2021 13:10, michael adams wrote:
"Michael Chare" wrote in message
...
On 02/03/2021 20:29, Chris Green wrote:
Tim+ wrote:
michael adams wrote:
Me and my neighbour both get a poor mobile signal. The sound is
distorted
even if rings my mobile from next door on his mobile. Quite
possibly it
only happens at certain times of day but we can not be certain,
as they
say. Would a decent mobile signal booster solve this?


Depending on your network, some providers will give/sell you a
device to
route calls through your own broadband via a picocell.

My sister has one as her house is in a mobile phone €œnot-spot€�
with abysmal
signal strength on all networks.

If your network doesnt have such devices, change to one that has.

They're getting more and more difficult to get nowadays

Yes, Wifi calling is the new way.

--
Michael Chare

Although we are close my phone can't pick up his wifi because the
walls insulation uses heat reflective metal foil.

Should I use a powerline adapter to bring the signal from his
router into my house?

powerline doesn't bridge houses. It barely works on one ring main


If he is agreeable, you should run an ethrnet cable from his house
to yours. In your house you could then used an old router
appropriately configured to broadcast the Wifi signal. There are
ethernet cables that are suitable for use outside.Â* In an ideal
world the device in your house should be a Wifi access point powered
by PoE from his house to avoid any risks from the properties being
connected to different power supply electrical phases.

Ethernet uses isolation transformers on inputs and outputs so there
is no possibility of electrical LF connection via a cat 5 cable for
precisely this reason. In offices having different rooms on different
phases is commonplace. In order to render Ethernet viable in such
spaces, the spec calls for mains isolated transformer coupled IO.

https://electronics.stackexchange.co...ically-coupled



Followup. Power over Ethernet BREAKS the safety of Ethernet by
transmitting DC power over the Ethernet, It is LESS safe than having
local power


PoE is used in offices. I would expect the equipment to conform to the
same or similar standard. It would make sense for the voltage to be
provided via the an isolating transformer in the RJ45 connecting chip.


You can't supply DC via a transformer



--
The lifetime of any political organisation is about three years before
its been subverted by the people it tried to warn you about.

Anon.

The Natural Philosopher wrote:

Michael Chare wrote:

The Natural Philosopher wrote:

Power over Ethernet BREAKS the safety of Ethernet by transmitting
DC power over the Ethernet, It is LESS safe than having local
power

PoE is used in offices. I would expect the equipment to conform to the
same or similar standard. It would make sense for the voltage to be
provided via the an isolating transformer in the RJ45 connecting chip.

You can't supply DC via a transformer

You don't need to; PoE uses a phantom* power arrangement so the DC is
applied across different twisted pairs, not within each twisted pair.

Equipment that recovers the power will pass the DC through a diode
bridge, not because there is any AC which needs rectifying, but just to
ensure correct polarity in case it has passed through a odd number of
crossover cables.


[*] ignoring the "dumb" PoE method that simply applies DC to the unused
pairs of 10/100 ethernet, but that doesn't use transformers either.

On 03/03/2021 15:52, The Natural Philosopher wrote:

Well I am not sure what VoLTE is, but wifi calling is not VOIP as
such, rather it is a way to connect to a normal mobileÂ* network across
the internet

Voice over LTE (Long Term Evolution, aka 4G)

https://www.4g.co.uk/what-is-volte/

On 04/03/2021 06:12, The Natural Philosopher wrote:
On 03/03/2021 19:44, Michael Chare wrote:
On 03/03/2021 15:01, The Natural Philosopher wrote:
On 03/03/2021 14:59, The Natural Philosopher wrote:
On 03/03/2021 14:51, Michael Chare wrote:
On 03/03/2021 13:10, michael adams wrote:
"Michael Chare" wrote in message
...
On 02/03/2021 20:29, Chris Green wrote:
Tim+ wrote:
michael adams wrote:
Me and my neighbour both get a poor mobile signal. The sound
is distorted
even if rings my mobile from next door on his mobile. Quite
possibly it
only happens at certain times of day but we can not be
certain, as they
say. Would a decent mobile signal booster solve this?


Depending on your network, some providers will give/sell you a
device to
route calls through your own broadband via a picocell.

My sister has one as her house is in a mobile phone €œnot-spot€�
with abysmal
signal strength on all networks.

If your network doesnt have such devices, change to one that has.

They're getting more and more difficult to get nowadays

Yes, Wifi calling is the new way.

--
Michael Chare

Although we are close my phone can't pick up his wifi because the
walls insulation uses heat reflective metal foil.

Should I use a powerline adapter to bring the signal from his
router into my house?

powerline doesn't bridge houses. It barely works on one ring main


If he is agreeable, you should run an ethrnet cable from his house
to yours. In your house you could then used an old router
appropriately configured to broadcast the Wifi signal. There are
ethernet cables that are suitable for use outside.Â* In an ideal
world the device in your house should be a Wifi access point
powered by PoE from his house to avoid any risks from the
properties being connected to different power supply electrical
phases.

Ethernet uses isolation transformers on inputs and outputs so there
is no possibility of electrical LF connection via a cat 5 cable for
precisely this reason. In offices having different rooms on
different phases is commonplace. In order to render Ethernet viable
in such spaces, the spec calls for mains isolated transformer
coupled IO.

https://electronics.stackexchange.co...ically-coupled



Followup. Power over Ethernet BREAKS the safety of Ethernet by
transmitting DC power over the Ethernet, It is LESS safe than having
local power


PoE is used in offices. I would expect the equipment to conform to the
same or similar standard. It would make sense for the voltage to be
provided via the an isolating transformer in the RJ45 connecting chip.


You can't supply DC via a transformer

You just have to use diodes to rectify it. On the router I looked at
there is a big transformer chip just before the RJ45 sockets.

I would think there must also be some electronics after the transformer
to make sure that the signal voltage is square rather than rounded.

--
Michael Chare

On 02/03/2021 18:45, michael adams wrote:
Me and my neighbour both get a poor mobile signal. The sound is
distorted even if rings my mobile from next door on his mobile. Quite
possibly it only happens at certain times of day but we can not be
certain, as they say. Would a decent mobile signal booster solve this?



I have both Vodafone and EE signal boosters .... what they do is give
you in effect a local cell, your phone connects to it by WiFi and it
routes your calls over Broadband.
Probably be discontinued in near future, as WiFi calling now supported.

Michael Chare wrote:

I would think there must also be some electronics after the transformer
to make sure that the signal voltage is square rather than rounded.

It's neither, it's flat.

On 04/03/2021 11:54, Andy Burns wrote:
Michael Chare wrote:

I would think there must also be some electronics after the
transformer to make sure that the signal voltage is square rather than
rounded.

It's neither, it's flat.

So how does it contain any information? For 100base-TX, on each pair,
the voltage varies between +1, 0 and -1.

--
Michael Chare

Michael Chare wrote:

Andy Burns wrote:

Michael Chare wrote:

I would think there must also be some electronics after the
transformer to make sure that the signal voltage is square rather
than rounded.

It's neither, it's flat.

So how does it contain any information?Â* For 100base-TX, on each pair,
the voltage varies between +1, 0 and -1.

We're talking about the power not the data ... the DC power is "imposed"
not directly on any given data pair, but between the data pairs.

On Thursday, 4 March 2021 at 11:53:56 UTC, rick wrote:
On 02/03/2021 18:45, michael adams wrote:
Me and my neighbour both get a poor mobile signal. The sound is
distorted even if rings my mobile from next door on his mobile. Quite
possibly it only happens at certain times of day but we can not be http://www.polqa.info/products.html
certain, as they say. Would a decent mobile signal booster solve this?

I have both Vodafone and EE signal boosters .... what they do is give
you in effect a local cell, your phone connects to it by WiFi and it
routes your calls over Broadband.
Probably be discontinued in near future, as WiFi calling now supported.

No, they use a 3G GSM transceiver, not WiFi.

John

Michael Chare wrote:
On 04/03/2021 11:54, Andy Burns wrote:
Michael Chare wrote:

I would think there must also be some electronics after the
transformer to make sure that the signal voltage is square rather
than rounded.

It's neither, it's flat.

So how does it contain any information? For 100base-TX, on each pair,
the voltage varies between +1, 0 and -1.


A GbE has eight wires, arranged as four differential pairs,
with transformer isolation at the source hardware, and
transformer isolation at the destination. This is a big big
improvement, over the shared coax cable scheme and vampire
tap used in the first networks.

___ ___________________ ___
\||/ \||/
/||\ /||\
\||/ \||/
___/||\___________________/||\___

___ ___________________ ___
\||/ \||/
/||\ /||\
\||/ \||/
___/||\___________________/||\___


___ ___________________ ___
\||/ \||/
/||\ /||\
\||/ \||/
___/||\___________________/||\___
| |
(+)---------+ +-------------- (+) phantom power received
___ ___________________ ___
\||/ \||/
/||\ /||\
\||/ \||/
___/||\___________________/||\___
| |
(-)---------+ +-------------- (-) phantom power received

You can apply a DC offset to the floating cable portion, because
it floats and has no effect on the data transmission going
on differentially on the pair, at relatively low amplitude.
The DC only appears between the two transformers, and neither end,
the data pads on the chips, don't see that DC voltage. The transformer
does not pass DC.

The transformers are also present, to reject common mode noise.
The wires in the Ethernet cable are twisted pairs. The
pairs are twisted, so that if an interference
source is present, the same noise signal is imposed on
both wires of the pair. The transformer "nulls" out the noise,
because A-B = 0. Both the A noise and the B noise are the same
amplitude, the transformer takes the difference, and zero noise
ends up at the destination.

If you use an oscilloscope and measure the "floating" noise on
a pair, I can easily see a 10V 60Hz signal on a wire in the cable,
in a lab situation. The transformer makes that disappear, by
taking the difference. At the time I first looked at that in
the lab, I was shocked by the sheer amplitude of the
signals I was seeing. The signals are not "real" in the sense
that you cannot extract a free lunch from the induced signal
and light up a lightbulb with it :-)

Now, if you run DC over the cable, like in the diagram, there's
a chance some noise could be induced on the wires. Maybe the
DC that is delivered, is not clean enough to use directly
for anything, but after being run through a DC regulation solution,
might be made a bit cleaner. It won't have my 10V AC signal
imposed on it either. The POE DC source will be stiff, and
the induced noise signal will have reduced amplitude.

The specs tell a story. They use high DC voltages at low
currents, and those can be converted, via a buck converter,
to a usable digital supply.

https://en.wikipedia.org/wiki/Power_over_Ethernet

Ethernet uses a Bob Smith grounding scheme, a ground plane
near the media end. It has 2kV capacitors, offering some
sort of ESD or induced lightning protection. (A "bit of protection",
not belt and suspenders. Your NIC could be blown to hell, in
spite of this scheme.)

(Page 86) SMSC LAN83C175
http://citeseerx.ist.psu.edu/viewdoc...=rep1&type=pdf

The transformer has some sort of breakdown voltage. The intention is,
to give a measure of induced HV protection. If there is a lightning
strike 100 feet from the house, your hope is, the floating bits
don't blow through and transfer an insult to the terminating equipment.
Maybe the portion around the transformer is damaged, and
"your NIC needs to be changed". If the onboard NIC on a desktop
is ruined, you can try installing a PCI Express x1 NIC in its place.
Laptops, not so much.

When I did an Ethernet at work on a computer board, one
of the other engineers mentioned the keyword I needed. I'd never
heard of Bob Smith before. (Ethernet hadn't been invented when I was
in school, and the very first Ethernet I did, used vampire taps
and wasn't nearly the same as the second one with the eight wire cable.
Bob Smith goes with the eight wire version.)

Paul

On 04/03/2021 08:55, Andy Burns wrote:
The Natural Philosopher wrote:

Michael Chare wrote:

The Natural Philosopher wrote:

Power over Ethernet BREAKS the safety of Ethernet by transmitting
DC power over the Ethernet, It is LESS safe than having local
power

PoE is used in offices. I would expect the equipment to conform to
the same or similar standard. It would make sense for the voltage to
be provided via the an isolating transformer in the RJ45 connecting
chip.

You can't supply DC via a transformer

You don't need to;Â* PoE uses a phantom* power arrangement so the DC is
applied across different twisted pairs, not within each twisted pair.

there are no spare pairs in gigabit ethernet

Equipment that recovers the power will pass the DC through a diode
bridge, not because there is any AC which needs rectifying, but just to
ensure correct polarity in case it has passed through a odd number of
crossover cables.



[*] ignoring the "dumb" PoE method that simply applies DC to the unused
pairs of 10/100 ethernet, but that doesn't use transformers either.

Like I said., POE doesnt use transformers


I think you missed the point. Ethernet is inherently isolated because it
uses transformers to couple input and output pairs.

POE inevitably breaks that isolation


--
Truth welcomes investigation because truth knows investigation will lead
to converts. It is deception that uses all the other techniques.

On 04/03/2021 11:50, Michael Chare wrote:
On 04/03/2021 06:12, The Natural Philosopher wrote:
On 03/03/2021 19:44, Michael Chare wrote:
On 03/03/2021 15:01, The Natural Philosopher wrote:
On 03/03/2021 14:59, The Natural Philosopher wrote:
On 03/03/2021 14:51, Michael Chare wrote:
On 03/03/2021 13:10, michael adams wrote:
"Michael Chare" wrote in message
...
On 02/03/2021 20:29, Chris Green wrote:
Tim+ wrote:
michael adams wrote:
Me and my neighbour both get a poor mobile signal. The sound
is distorted
even if rings my mobile from next door on his mobile. Quite
possibly it
only happens at certain times of day but we can not be
certain, as they
say. Would a decent mobile signal booster solve this?


Depending on your network, some providers will give/sell you a
device to
route calls through your own broadband via a picocell.

My sister has one as her house is in a mobile phone €œnot-spot€�
with abysmal
signal strength on all networks.

If your network doesnt have such devices, change to one that
has.

They're getting more and more difficult to get nowadays

Yes, Wifi calling is the new way.

--
Michael Chare

Although we are close my phone can't pick up his wifi because the
walls insulation uses heat reflective metal foil.

Should I use a powerline adapter to bring the signal from his
router into my house?

powerline doesn't bridge houses. It barely works on one ring main


If he is agreeable, you should run an ethrnet cable from his house
to yours. In your house you could then used an old router
appropriately configured to broadcast the Wifi signal. There are
ethernet cables that are suitable for use outside.Â* In an ideal
world the device in your house should be a Wifi access point
powered by PoE from his house to avoid any risks from the
properties being connected to different power supply electrical
phases.

Ethernet uses isolation transformers on inputs and outputs so there
is no possibility of electrical LF connection via a cat 5 cable for
precisely this reason. In offices having different rooms on
different phases is commonplace. In order to render Ethernet viable
in such spaces, the spec calls for mains isolated transformer
coupled IO.

https://electronics.stackexchange.co...ically-coupled



Followup. Power over Ethernet BREAKS the safety of Ethernet by
transmitting DC power over the Ethernet, It is LESS safe than having
local power

PoE is used in offices. I would expect the equipment to conform to
the same or similar standard. It would make sense for the voltage to
be provided via the an isolating transformer in the RJ45 connecting
chip.


You can't supply DC via a transformer

You just have to use diodes to rectify it.Â* On the router I looked at
there is a big transformer chip just before the RJ45 sockets.

transformers do not come in chips

I would think there must also be some electronics after the transformer
to make sure that the signal voltage is square rather than rounded.

Christ on a bike....


--
A lie can travel halfway around the world while the truth is putting on
its shoes.

The Natural Philosopher wrote:

Andy Burns wrote:

The Natural Philosopher wrote:

You can't supply DC via a transformer

You don't need to;Â* PoE uses a phantom* power arrangement so the DC is
applied across different twisted pairs, not within each twisted pair.

there are no spare pairs in gigabit ethernet

We're not talking about the spare pairs, that was the "dumb" scheme I
mentioned, "proper" PoE doesn't need separate pairs for data and power.

Equipment that recovers the power will pass the DC through a diode
bridge, not because there is any AC which needs rectifying, but just
to ensure correct polarity in case it has passed through a odd number
of crossover cables.

[*] ignoring the "dumb" PoE method that simply applies DC to the
unused pairs of 10/100 ethernet, but that doesn't use transformers
either.

Like I said., POE doesnt use transformers

Not sure we're saying the same thing.

I think you missed the point. Ethernet is inherently isolated because it
uses transformers to couple input and output pairs.

POE inevitably breaks that isolation

depends whether the PSU itself is isolated?

The Natural Philosopher wrote:

Michael Chare wrote:

On the router I looked at there is a big transformer chip just
before the RJ45 sockets.

transformers do not come in chips

https://uk.rs-online.com/web/p/lan-ethernet-transformers/1353928

On 05/03/2021 07:06, Andy Burns wrote:
The Natural Philosopher wrote:

Michael Chare wrote:

On the router I looked at there is a big transformer chip just
before the RJ45 sockets.

transformers do not come in chips

https://uk.rs-online.com/web/p/lan-ethernet-transformers/1353928
Not a chip. DIL package, but not a 'chip'


--
€œIt is not the truth of Marxism that explains the willingness of
intellectuals to believe it, but the power that it confers on
intellectuals, in their attempts to control the world. And since...it is
futile to reason someone out of a thing that he was not reasoned into,
we can conclude that Marxism owes its remarkable power to survive every
criticism to the fact that it is not a truth-directed but a
power-directed system of thought.€�
Sir Roger Scruton

The Natural Philosopher wrote:
On 04/03/2021 08:55, Andy Burns wrote:
The Natural Philosopher wrote:

Michael Chare wrote:

The Natural Philosopher wrote:

Power over Ethernet BREAKS the safety of Ethernet by transmitting
DC power over the Ethernet, It is LESS safe than having local
power

PoE is used in offices. I would expect the equipment to conform to
the same or similar standard. It would make sense for the voltage to
be provided via the an isolating transformer in the RJ45 connecting
chip.

You can't supply DC via a transformer

You don't need to; PoE uses a phantom* power arrangement so the DC is
applied across different twisted pairs, not within each twisted pair.

there are no spare pairs in gigabit ethernet

Equipment that recovers the power will pass the DC through a diode
bridge, not because there is any AC which needs rectifying, but just
to ensure correct polarity in case it has passed through a odd number
of crossover cables.



[*] ignoring the "dumb" PoE method that simply applies DC to the
unused pairs of 10/100 ethernet, but that doesn't use transformers
either.

Like I said., POE doesnt use transformers


I think you missed the point. Ethernet is inherently isolated because it
uses transformers to couple input and output pairs.

POE inevitably breaks that isolation

The voltage on POE (~40VDC or more), implies an
additional level of SMPS is used at the destination.
Nobody wants to build logic running at 40VDC.

It is at that point, that isolation can be added if
desired.

A buck converter doesn't offer isolation. It has
one magnetic for energy storage, and is ground
referenced.

Whereas an SMPS with transformer isolation, and
classical rectification on the secondary, that
has a withstanding rating provided by the transformer.
On an ATX supply, that withstanding is somewhere on
the order of 1100V or so. And is also why the ATX supply
has a sticker on it announcing "HIPOT tested". Which
means each unit receives a test to prove it can withstand
a voltage near that value, for some number of seconds or
minutes. And that the primary and secondary really are
isolated.

You can put a smaller version of that, inside a POE powered item.

Even the original Ethernet had power isolation. For the
cable feeding the brick transceiver from 3COM. I don't
know if much remains on the web about that stuff.

Paul