10BASE5 (also known as thicknet) is the original "full spec" variant of Ethernet cable, using special cable similar to RG-8/U coaxial cable. This is a stiff, 0.375-inch (9.5 mm) diameter cable with an impedance of 50 ohms (Ω), a solid center conductor, a foam insulating filler, a shielding braid, and an outer jacket. The outer sheath is often yellow-to-orange/brown foam fluorinated ethylene propylene (for fire resistance) so it often is called "yellow cable", "orange hose", or sometimes humorously "frozen yellow garden hose".
10BASE5 has been superseded by other cabling and wireless networking media, though due to its original widespread deployment may still be in use in some installations.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 base-band signaling as opposed to broadband, and the 5 stands for the maximum segment length of 500 meters (1,600 ft).
The maximum practical number of nodes that can be connected to a 10BASE5 segment is limited to 100 and transceivers may be installed only at precise 2.5-meter intervals. This distance was chosen to not correspond to the wavelength of the signal; this ensures that the reflections from multiple taps are not in phase. These suitable points are marked on the cable with black bands. The cable must be one linear run; T-connections are not allowed. A 50-ohm resistive terminator is required at each end of the cable.
Transceivers can be connected to cable segments with N connectors, or via a vampire tap, which allows new nodes to be added while existing connections are live. A vampire tap clamps onto the cable, forcing a spike to pierce through the outer shielding to contact the inner conductor while other spikes bite into the outer braided shield. Care must be taken to keep the outer shield from touching the spike; installation kits include a "coring tool" to drill through the outer layers and a "braid pick" to clear stray pieces of the outer shield.
The transceivers connect to nodes using a connector called an Attachment Unit Interface (AUI), a 15-pin, two-row D-style connector, but using a sliding clip instead of screws for cable restraint. A multi-wire cable carries the connection between the transceiver and the node.