The thin coaxial cabling used for 10Base2 installations of Ethernet networking. Thinnet cabling is RG-58 coaxial cabling that is 3/16 inch in diameter and has an impedance of 50 ohms. Thinnet uses BNC connectors to connect cable segments, computers, and concentrators (hubs). Many older hubs, bridges, routers, and other networking devices have at least one thinnet port for connecting to 10Base2 networks. Thinnet was often used in the 1980s for workgroup or departmental local area networks (LANs); it has largely been replaced by unshielded twisted-pair (UTP) cabling.
Thinnet cables must be terminated at both ends. If communication is down, check the termination points, and then check for loose BNC T-connectors attached to the computers on the network. Thinnet cabling can become damaged if it is sharply bent or twisted, so handle it carefully. (It is not nearly as fragile as fiber-optic cabling, however.)
One place where thinnet is still useful is in electrically noisy environments such as shop floors in factories, where electromagnetic interference (EMI) caused by motors, generators, and other heavy equipment can disrupt communication over UTP. Coaxial cabling, with its internal shielding, can easily withstand the noise.