There are different versions of 802.3, depending on the type of cabling used. The IEEE standard for Thick Ethernet is 10Base5 and for Thin Ethernet is 10Base2. This method allows multiple users to access the network through a common cable. If no signals are present the transmission is sent. If a signal is detected then transmission is delayed.
Collision detection is applied when two or more devices transmit at the same time.
The same occurs in the event of a collision. A device knows if a collision occurred when it does not receive its own transmission back. There are two topologies used with an Ethernet network and they are bus and star. Bus topology is used by 10 Base5 and 10 Base2. It consists of a shared common cable with a 50ohm terminator connected to each end.