The LEDs of the PoE detector indicate the following things:
1. What kind of PoE is transmitted over the LAN cable? A distinction is made between passive PoE with 24 volts, passive PoE with 48 to 56 volts, the IEEE802.3af (PoE) standard and the IEEE802.3at (PoE) standard.
2. Which pinout mode is used? The detector shows you whether pinout mode A, mode B or mode B with reversed polarity is used.
In addition, you do not need batteries, the detector itself is supplied with power via PoE and it fits in your pocket.