Siemens SCALANCE X101-1 Operating Instructions Manual page 19

Two components connected to a link segment can exchange information about the data
transfer and can adapt their settings to each other. The mode with the highest possible
speed is set.
Note
Devices not supporting autonegotiation must be set permanently to 100 Mbps half duplex or
10 Mbps half duplex.
Auto polarity exchange
If the pair of receiving cables is connected incorrectly (RD+ and RD- interchanged), the
polarity is adapted automatically.
MDI / MDI-X autocrossover function
With the MPI/MDI-X autocrossover function, the send and receive contacts of an Ethernet
port are assigned automatically. The assignment depends on the cable with which the
communications partner is connected. This means that it does not matter whether the port is
connected using a patch cable or crossover cable. This prevents malfunctions resulting from
mismatching send and receive lines. This makes installation much easier for the user.
The SCALANCE X-100 media converters all support the MDI / MDI-X autocrossover
function.
SCALANCE X-100 media converter
Operating Instructions, 04/2016, C79000-G8976-C346-02
Description of the device
3.3 TP ports (twisted pair)
19