FWIW, all of my devices – Windows computers, wired or wireless, Android tablet, Android phone – make it very clear what the connection issue is. The wireless devices universally display either a grayed-out icon with an “X” through it (IIRC) if there’s no wireless connection, or a wireless icon with an exclamation mark over it, meaning wireless is fine, but the router has no internet connection (or it might be interpreted to mean that the router has found a particularly exciting internet connection! 
) It would seem to me that someone would have to be quite inexperienced or clueless to not see the difference between “connection to router is fine” but “the router has no internet access”.
For your own use, sure, anything goes. You can use red for a negative jumper cable, put batteries in parallel, put the potable water in the red jerry cans. But a manufacturer must anticipate end users will make assumptions about familiar connector types.
Well, there are ways to make it safe. Want to use Ethernet cables for power only? Go ahead: just make sure you use the Power-over-Ethernet protocol, which has all the required measures for ensuring a safe connection. Or use it for your own custom data protocol, as long as the device can accept Ethernet signals without damage and never sends a signal that Ethernet isn’t resilient enough to receive.
I like these sorts of threads, as they help me learn basic home level IT stuff. Used to think I was clever with cable ends, I was pleasantly surprised when my first “ethernet cable” termination worked correctly last year. YouTube tutorials were VERY helpful (done in the dirt, on my back in the crawlspace of a a100 yr old house).
I have an OBRI router setup (6 satellites) that doesn’t like the old walls here, and I just found out this week I can use the OLD cable running through all the walls. Will require some juggling of things……but COX drops our speeds down enough that satellites cant talk to each other. So Ive been studying MoCa network adapters, (they use the old coaxial cable) which would really help close the distance for the routers. The owners also pay for the lowest tier for Mbs, which IMO, doesn’t give enough capacity when other big users get busy. Speeds are nomally 100mbps and above, but when they drop to to under 10mbps, nothing works very well. Except my speed tester on my phone!!!
As you can tell, Im out of my depth, but my employers and I don’t seem to trust anyone but ourselves anymore……we all love the concept of “plug n play”…..(if I have to start programming anything here other than a new TV, Im done for, back to the gardens I go 
Slight hijack, but I thought the related idea of using coaxial data cables for power was quite convenient and elegant. One of the most useful examples is the use of the same coax that connects a DTH satellite dish to the IRD receiver to supply power to the LNB at the dish, the power coming from the receiver itself. Also, cable companies routinely use their own coax to connect power adapters to devices like powered splitters. Why not? It’s low voltage, and if there’s one thing they have, it’s lots of coax! I’m currently using a run of coax to provide power to a UHF television antenna amplifier.
I find it interesting that power-over-coax works. But I haven’t really thought about that problem at all.
PoE works because there are 4 differential pairs. Each pair doesn’t care about what voltage it runs at since the transceivers only care about the difference, and being a twisted pair, they reject common mode noise. So you can set two pairs for positive voltage and two for ground. Or 1+1 if your cable only has two pairs total.
I guess since the coax is AC coupled, the voltage difference between the core and shield doesn’t really matter.
This had been my question.
If LEGO is using RJ45 connectors, did they design all their devices and protocols so plugging them into Ethernet with or without PPOE won’t wreak havoc on the LEGO device or whatever is at the other end of the wire? One would hope so, but this one doesn’t know for sure.
Many people are in fact quite clueless.
I do know that plugging motors into sensor ports or vice-versa won’t actually break anything: It just won’t work. I would imagine the same would be true if you plugged a Lego component into a router or something, but I’ve never tried it.
Still, it probably would be more user-friendly if it were simply not possible to plug a motor into a sensor port. I’ve certainly seen my share of student projects where that was the problem.
For sure one of the basics of design for safe assembly is to make it nearly impossible to assemble your [whatever] wrong. Each cable has a different connector or a different length so no wrong connections can be made. Either all screws or bolts are the same length, or those of different length are also different diameter. etc.
IOW, make Murphy really work for it to achieve his mischief.
For sure that can really increase costs. So maybe not really a good trade for a hobby kit of modular components.
This. I’ve worked for over 30 years in IT, often doing support, and “My internet is down” can mean anything, from a loose cable up to a burning office…
This is one of those things (actually, reality is like this all the time) where the name of a thing is not a precise recipe for the thing. They’re generally patch cables, ethernet cables or network cables - CAT(something) in cases where the (something) is an important distinction. I can’t think of a context where it’s very likely someone would not understand what you want if you ask for a patch cable.
The only terminology I’ve heard used for them that made me do a double-take was ‘WiFi cable’ - yes, apparently some people call them that, because reasons.
I suppose the reason would be that people young enough to know Wifi as the default network connection use that word when they see a machine with a wired network connection for the first time.
Yeah, ‘WiFi’ has just become somewhat synonymous with ‘Internet connection’
Back in the 1990s when I first used Ethernet cables, a ‘patch cable’ was a specific type of Ethernet cable and it was important to specify it - because it was not a ‘crossover cable’, a crossover cable being one where the transmit wire pair was connected to the terminals for the receive wire pair on the other end, and vice versa, while a ‘patch cable’ was connected 1:1. Nowadays this is not significant; AFAIK modern Ethernet chips make sense of the other party’s use of wires on the fly.
Without any context, patch cable would be a 1/4" audio cable, like used between an electric guitar & amp or what an early telephone switchboard operator was seen using.
I have a few shortwave transmitter couplers which are used to electrically compensate a given antenna for use across a large section of RF band. They’re more commonly called autotuners, mine are 1.6-30 MHz, and have a sophisticated PCB with processors, memory, controls for switching in banks of capacitors and coils. They connect to their radios with plain coax which carries DC power as well as the large 125 Watt transmit signal but also the tiny received signal from distant stations. Neat tech, this one is meant to be bumper mounted, though I’ve only set it up temporarily in the past.
I don’t know either, but it’s not too hard to get right. All pairs already go through coupling transformers, so as long as the voltages are kept within spec, it’s hard to damage something even with an ad-hoc implementation of PoE. And they’re all backwards compatible, so even though the transmit voltages have mostly gone down over time, any receiver still needs to be tolerant of a 5v difference on the wires.
In practice I’d just drop some off-the-shelf solution down, since they’re cheap and they’ve already solved these problems. But even if they did everything custom, it’s not that hard to tolerate being compliant to anything that might be on the other end, as well as not sending anything that the other end can’t tolerate.
On a somewhat related note, when helping my parents figure out why my parents were going over they cellular data limit every month, it became evident that they didn’t understand that the fact that WiFi is turned on in their phone’s settings doesn’t necessarily mean it’s actually connected their home WiFi network (or any WiFi network). They didn’t realize they needed to take additional steps to select a network to connect to and then log in to that network. Thus they were unknowingly all their cellular data with all the web surfing they were doing at home.
My parents, and also some people my age don’t understand that difference, either. It isn’t a big issue though, because my father has a dumb phone without data anyway and my mother’s smart phone is configured to switch smoothly between their home wifi and cell data when on the road.
There’s also quite a lot of variance in terms of how different devices and operating systems deal with “wifi is good but internet is down” scenarios. Some will show a different wifi icon, others will disconnect you, others will try to show you a captive portal to login from, others will just do nothing.
Especially in the phone era, the wifi symbol superficially resembles the other main signal symbol – the cellular connection strength – but whereas “cell signal’s good” almost always means “internet works too”, that is definitely not the case with wifi.
Unless you grew up in that era where the wifi router is a separate piece of equipment from the internet modem (and they almost never are anymore; most ISPs provide all in one modem-router-access points now), it would not be obvious that the wifi connection is something different from the internet connection. It makes sense to us oldies, but not necessarily to the kids or ancient ones…
No, at least in my experience, it’s device-dependent, regardless of the router/modem integration. My Windows computers and my tablet both distinguish between “router has no internet access” and “no wired or wireless access to the router at all”.