IMO live demo is better in some cases, but if there are complicated or time-consuming steps where the prerequisite can not be met quickly, a recording would be better
This is horrible news. Zigbee has been trouble-free and Thread has been nothing but Trouble to the point I had to throw out everything based on Thread…
some of the tests and standard answers are strange such as the one with debounced function not considering whether there should only be 1 arg / the dev could use the arguments keyword and call, the filter numbers question insisting on === instead of == etc etc.
Agreed, if it's not your primary purpose for having the account then it should be fine. I did a bunch of FX through them not long after opening mine, and they sent me a polite email telling me that I shouldn't do that, which was fair enough. Much better than the "freeze account first, warn later" attitude that many other financial companies seem to have.
Now that I've been investing with them for a while, they don't seem to mind.
Yes, but passive PoE is almost universally at 24v, and per the Ethernet spec (as quoted above) an Ethernet PHY should tolerate 24v fine. This is important as transients from nearby lightning or occasionally even coupling to power cables can produce this kind of voltage. Ethernet connectors are magnetically coupled for protection from these transients.
The problem with PPoE in these cases is, I think, not the voltage so much as the current. The continuous 24v supply may overheat the magnetic coupling transformer and cause it to fail. Some Ethernet interfaces, usually on telecom equipment and quality switches, have over current protection to prevent this. Unfortunately consumer devices usually don't.
It's important to understand this because 802.3af etc. does provide power without being asked - as a rest for a characteristic resistance on the receiver. Otherwise it wouldn't know if a PoE-capable device was connected. Up to 20v can be applied during this process but it is time limited. In general, 802.3 PoE supplies must monitor the current usage of the powered device and cut off power if it is too high or even too low for more than a short period of time. This is in part to prevent this overheating problem on devices that might, for some coincidental reason, fall into the appropriate resistance range to activate PoE.
In other words, 24v or even hundreds of volts for a few seconds is perfectly safe. 24v for minutes is likely to cause damage to devices without better protection than the spec requires. Old Ethernet equipment used to make the non-isolated components relatively easy to replace so that repairs after a problem like this were easier but now the isolation is a tiny surface mount part and replacing it will require tools and skill.
Looks like PoE uses pin 4 and 5 for +48V, and 7 and 8 for GND, which respectively are pair C and D of GbE. On ISDN, pinout could vary but one I could find said 1-2, 4-5 for V+ and 3-6, 7-8 for V-. In either cases, both sides of isolation magnetics are connected to pins of same potential and current is only proportionate to voltage imbalance within each pair which should be minuscule.
I wonder if the problem is that 1:1 signal transformers for decoupling are being replaced with simple DC blocking circuit. That can be most simply done with a spare 0.1uF and an R10k per pin, which by the way generate load of from V/R=I 48V/10kohm = 5mA and 48V * 5mA = 230mW > 1/6W. That could cause resistor to burn off if phone-sized components would be used. Or if the cap might only be rated for 10V, it could burn open. I have nothing to support these hypothesis though. I could be entirely off.
Also I suspect the "passive PoE" mentioned above could be cheap injectors with very rounded corners and always active 48V. Those are widespread for surveillance cameras and other neckbeardy applications.
> Looks like PoE uses pin 4 and 5 for +48V, and 7 and 8 for GND, which respectively are pair C and D of GbE.
There's three common pin outs. You've described 'alternate B' -- the unused pairs of 10/100; you can also use 'alternate A', using the pairs used for 10/100. Or 4-pair would have both.
