PROTOCOL SOFTWARE AND ETHERNET WIRING:
All wiring methods use identical Ethernet specifications. e.g. they need same message format. They need same CSMA/CD algorithems. They may mix different methods in an Ethernet.
NICs can give all three-connection technologies. The protocol software can't distinguish among wiring methods. The NIC is given in the figure below with three connectors.
They are needed for extension of connection with multiplexing concept. They are sometimes known Ethernet-in-a-box. It is effectively a very minimized Ethernet with very maximized AUI cables. It can be connected into bigger Ethernet.