Questions regarding possible dangers of connecting non-active PoE devices to the TSW202 switch

[ttnkftw]

Hi.

I apologize if these are noob questions but better to ask than be sorry.

So as I understand it, Teltonika devices like the TRB140 cannot be powered via an active PoE port like the switch TSW202 has. This is specified on the wiki for the TRB140 and there have been already some poor souls who have unfortunately made this mistake:

TRB140 connected to TSW200 .... and broken!

Hello, I “had” an TRB140 and suppose “still” have an TSW200 (POE). The TSW200 (POE) was supplied with 48Vcc and the TRB140 (batch 062) with 24Vcc from industrial power supplies from MeanWell. The Ethernet connection between them destroyed the TRB140. At least the QT24A12 Gigabit 1000 BASE-T Ethernet Transformer Module it smells like smoked. The specification from this embedded transformer its for NON POE Ethernet. Your specification for TRB140 is that “TRB140 devices support POE from HW revis…

TRB140 died after connecting to TSW100 - Crowd Support Forum | Teltonika...

(If Teltonika is open to ideas, maybe they could put some sticker over the TRB140 ethernet port explicitly saying you should not connect it to an active PoE port - just a suggestion as this was not immediately clear to me as well.)

1. But, if the TRB140 device is already connected to a power socket then there should be no problem with connecting it via the ethernet cable to one of the PoE ports afterwards, as the following text suggests, correct?

The power socket has higher priority meaning that the device will draw power from the power socket as long as it is available. When the device is switching from one power source to another it loses power for a fraction of a second and may reboot. The device will function correctly after the reboot.

2. However, what happens if there is a power outage on the TRB140 side (e.g. someone unplugs it from the power socket)? Can the switch damage the device then, or will there be no damage until the ethernet cable is unplugged and plugged to the switch again while the TRB140 is still not plugged into a power socket? Which would mean that one should always make sure the TRB140 device is powered on from the electrical grid before the switch is turned on if I understand this correctly.

3. If my assumptions from 2) are correct, what can one do to prevent possible damage in case the switch is turned on before the TRB140 device? An obvious answer could be turning off PoE on the Network > Ports > Ports Settings page for the specific port, and/or putting a PoE splitter before the TRB140 device so there can be no chance that the device will receive any power from the active PoE port ever.

4. And last question - I think I already unknowingly verified this by experiment but it seems that if a connected device (e.g. a computer) does not support any kind of PoE on its ethernet port then there should be no danger at all - correct?

Thanks for your time.