Short for the bayonet nut connector, the BNC interface is a connector for coaxial cables. The BNC interface (a basic NIC) is a 10BASE-2 connector also known as the coaxial thin cable connector, which can isolate the video input signal and depress the interference between the signals. Besides, its signal bandwidth is larger than that of the ordinary 15-pin D-type interface to achieve a better signal response effect. The network card of the BNC interface shall be used in match with the Ethernet over BNC or the Token Ring whose transmission medium is the thin coaxial cable. The reason for the rare Ethernet over BNC chiefly is that networks seldom adopt thin coaxial cables as the transmission medium. Now, the dominant practice is the video signal transmission of monitors in security industry.
The BNC interface has never been out of date for the coax is a shielded cable advantaged with a long transmission distance and an excellent signal stability. At present, it is still widely used in the communication system. Examples are that the E1 interface in network equipment is connected by two coaxial cables with BNC interface and that audio and video signals transmission tasks are performed by the coax in advanced monitors and audio equipment.