Applications
CSMA/CD was used in now obsolete shared media Ethernet variants (10BASE5, 10BASE2) and in the early versions of twisted-pair Ethernet which used repeater hubs. Modern Ethernet networks built with switches and full-duplex connections no longer utilize CSMA/CD though it is still supported for backwards compatibility. IEEE Std 802.3, which defines all Ethernet variants, for historical reasons still bears the title "Carrier sense multiple access with collision detection (CSMA/CD) access method and physical layer specifications".
Variations of the concept are used in radio frequency systems that rely on frequency sharing, including Automatic Packet Reporting System.
Read more about this topic: Carrier Sense Multiple Access With Collision Detection