Siemens 3RS2 Manual page 51

Option 2: Direct voltage supply with 24 V DC
If no master is available, you can operate the IO-Link device with a 24 V DC voltage source.
For this purpose, connect the IO-Link device with the voltage source via the two cables L+ and
L-. Since cable C is not used in this case, communication via IO-Link is not possible.
The pin assignments of the available IO-Link devices are described in the relevant product
chapters.
3RS2 temperature monitoring relay
Equipment Manual, 02/2022, A5E42462552002A/RS-AB/002
Digital devices with IO-Link
6.3 Connection options for IO‑Link
51