For a direct connection between PC and OMNIALOG, the right cable to use is a CROSSED cable.
However, it could happen that also using a STRAIGHT LAN cable, it is possible to establish the connection with OMNIAlog. This occurs because from 2011 it has been realized a function called Auto-MDIX, that is available on some Ethernet (NIC) network cards. Auto-MDIX is a physical auto-sensing directly implemented on the NIC of the used PC. Furthermore, on this PC it has to be installed the specific driver of the same card. This is necessary because with the generic drivers of Microsoft Windows this function couldn’t work correctly despite it is on the NIC.
To understand if the NIC supports the Auto-MDIX it is necessary to verify it on the technical sheets of the used PC.
Anyway, it is possible to generalized saying that if a PC works with Microsoft Windows 7 or Microsoft Windows 8 (and any hardware post 2011), it has this function enabled in the 90% of cases. Pay attention if you own a PC with Microsoft Windows XP as operating system.