POE is a good bit of a mess. Here is my take on it after an investigation which took way too long. So no question but please correct where wrong:
TSW202 specifies poe ‘quote wiki’:
This device uses PoE alternative B.
PoE Alternative A for TSW202 was introduced earlier batches (see below) used PoE Alternative B:
802.3af and 802.3at Alternative A (Batch 15 and all batches from Batch 17 onward)
802.3af and 802.3at Alternative B (Batches 1–14 and Batch 16)
So it seems tt has settled at Alternative A.
According to wikipedia 802. af:
The Power Sourcing Equipment (PSE), not the Powered Device (PD), decides whether Mode A or Mode B shall be used. PDs that implement only Mode A or Mode B are disallowed by the standard.[37] The PSE can implement Mode A, Mode B, or both (4-pair mode). A PD indicates that it is standards-compliant by placing a 25 kΩ resistor between the powered pairs. If the PSE detects a resistance that is too high or too low (including a short circuit), no power is applied. This protects devices that do not support PoE.
Hence, TSW202 is a PSE and allowed to choose A or B mode (latest batches using A). It is the PD which should be compliant to 802.af to prevent ‘fireworks’.
And there is a problem because a lot af tt’s own stuff (and others) can use poe as PD but is NOT 802.af compliant using passive POE alternative B. Sometimes it simply does not work (mismatch mode a/b wirting) but bad luck ‘fireworks’ when 57V 802.af is put at a 24V poe passive device…
Another problem is findig out which of the flavours is used by your PD to prevent frying… di I dare to connect it to this lottery?
I leave it here as a note to myself.
(TT doc seems reasonable accurate, no blame to them, this poe thing is just a mess imho)
Thank you for reaching out to us regarding PoE behaviour on your TSW202 switch. I will try to address your concerns one by one to help you ensure proper PoE deployment.
Confirm Your TSW202 PoE Alternative
• The TSW202 supports IEEE 802.3af and 802.3at PoE+ standards. Depending on hardware batch, the switch uses either PoE Alternative A or Alternative B.
– Alternative B is used on earlier production batches.
– Starting with newer revisions (from late 2024), the default PoE has been transitioned to Alternative A to improve compatibility with connected devices.
You can find the batch number in the device’s WebUI in Status → System in the device section you should be able to see the batch number.
Match PoE Standard with Powered Devices
• Ensure that your powered devices (PDs) support the same PoE alternative as the TSW202’s current hardware revision.
• If a PD supports both alternatives or standard 802.3af/at negotiation, it will interoperate correctly regardless of alternative.
• Devices that only accept one specific alternative or rely on non‑standard/passive PoE may not power up reliably.
This alignment is essential because PoE negotiation and power delivery follow the IEEE standard behaviour defined for the PSE and PD roles.
Use Official Documentation for Reference
• The Teltonika Networks Wiki Quick Start Guide for TSW202 details the PoE alternatives associated with specific batch ranges.
• Product Change Notifications document the intentional shift to Alternative A in newer hardware revisions for broader device compatibility.
We recommend referencing these sources when planning deployments or specifying units for customer solutions.
Quick start guide:
Product change notifications:
Select Compatible Equipment or Use Converters If Required
• If your PDs only support the opposite PoE alternative, consider either:
– Using a TSW202 from a batch with the matching PoE alternative, or
– Adding a PoE alternative A↔B converter at the PD side.
Please note that Teltonika does not currently offer a dedicated PoE switch that simultaneously supports both alternatives natively.
Please let me know if you have any additional questions,