10BASE5

10BASE5 (also known as thick Ethernet or thicknet) was the first commercially available variant of Ethernet. 10BASE5 uses a thick and stiff coaxial cable up to 500 metres (1,600 ft) in length. Up to 100 stations can be connected to the cable using vampire taps and share a single collision domain with 10 Mbit/s of bandwidth shared among them. The system is difficult to install and maintain.

10BASE5 was superseded by much cheaper and more convenient alternatives: first by 10BASE2 based on a thinner coaxial cable, and then once Ethernet over twisted pair was developed, by 10BASE-T and its successors 100BASE-TX and 1000BASE-T. As of 2003, IEEE 802.3 has deprecated this standard for new installations.

The name 10BASE5 is derived from several characteristics of the physical medium. The 10 refers to its transmission speed of 10 Mbit/s. The BASE is short for baseband signalling (as opposed to broadband), and the 5 stands for the maximum segment length of 500 metres (1,600 ft).

For its physical layer 10BASE5 uses cable similar to RG-8/U coaxial cable but with extra braided shielding. This is a stiff, 0.375-inch (9.5 mm) diameter cable with an impedance of 50 ohms, a solid center conductor, a foam insulating filler, a shielding braid, and an outer jacket. The outer jacket is often yellow-to-orange fluorinated ethylene propylene (for fire resistance) so it often is called "yellow cable", "orange hose", or sometimes humorously "frozen yellow garden hose". 10BASE5 coaxial cables had a maximum length of 500 metres (1,600 ft). Up to 100 nodes could be connected to a 10BASE5 segment.

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