10BASE5

10BASE5 (also known as thick ethernet or thicknet) is the original "full spec" variant of Ethernet cable, using cable similar to RG-8/U coaxial cable but with extra braided sheiding.

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.

ThickNet, also known as 10BASE5 or IEEE 802.3-1985, is an Ethernet standard that requires a specialized coaxial cable to transmit Ethernet frames at a rate of 10Mbps. It derives its nickname, which is a portmanteau of "Thick Ethernet," from the thick coaxial cable it uses, which is 0.375 inches in diameter.

The designation 10BASE5, assigned to the ThickNet standard by the Institute of Electrical and Electronics Engineers, provides a quick summary of the characteristics of its physical medium:

"10" denotes its maximum data transmission rate of 10Mbps;

"BASE" is shorthand for "baseband transmission," meaning the medium exclusively transmits Ethernet signals; and

"5" means that it can transmit data at a maximum length of 500 meters before it experiences signal degradation.

The specialized coaxial cable used for a ThickNet computer network is sometimes referred to as "yellow cable" or "orange cable" because its outer insulation or jacket is made of either PVC (yellow) or Teflon (orange). This material makes the cable stiff and inflexible.

The cable contains a solid center conductor, and surrounding this conductor is an insulating filler made of foam, as well as a shielding braid. The cable must have a characteristic impedance of 50 ohms. Examples of coaxial cables made specifically for Ethernet include Belden numbers 9880 and 89880. ThickNet may also make use of RG-11 coaxial cable.

ThickNet employs a bus configuration as its network topology, meaning all nodes or devices are connected in a linear manner to one cable, known as a backbone, with 50 ohm resistive terminators at each physical end of the network. No more than 100 nodes may be connected to a ThickNet segment.

Transceivers, also known as Medium Attachment Units (MAU), were widely used in ThickNet networks. The term "transceiver" is a portmanteau of "transmiter" and "receiver," meaning it could both transmit and receive signals.

Transceivers were connected directly to cables through a device known as a "vampire tap," which is called such since it has spikes that pierce directly through the cable's outer jacket and into its center conductor. An N connector may also be used to connect a transceiver to a cable.

An Attachment Unit Interface (AUI) cable is used to connect a transceiver to a node. Transceivers may only be installed every 2.5 meters in order to not correspond to the wavelength of the signal. This minimizes echo and ensures that the reflections from multiple taps are not in phase.

ThickNet is the original Ethernet specification, although it was quickly superseded by 10BASE2 (also known as "ThinNet"). At present, it is considered obsolete computer networking technology.

Network design

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-metre 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.