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Katherine Johnson’s mathematical calculations helped guide some of America’s most important early space missions while she confronted the racial and gender barriers faced by Black women in twentieth-century America.
MORE →Reflects the personal views, recollections, and perspective of the author, Mike Davis.
This is a personal recollection on the Move fire on May 13, 1985
10BASE5 (also known as thick Ethernet or thicknet) is a version of Ethernet providing 10 Mbit/s bandwidth over a thick coaxial cable having a maximum length of 500 m (1,600 ft). It was the first commercially available version of Ethernet. The technology was standardized first by Ecma International in early 1982 based on an IEEE draft standard, then by IEEE in 1983 as IEEE 802.3.[1][2] Up to 100 stations can be connected to the cable in a single collision domain. The standard specifies CSMA/CD to resolve collisions.
10BASE5 was superseded by much cheaper and more convenient alternatives: first by 10BASE2 based on a thinner coaxial cable (1985), and then, once Ethernet over twisted pair was developed, by 10BASE-T (1990) and its successors 100BASE-TX and 1000BASE-T. In 2003, the IEEE 802.3 working group deprecated 10BASE5 for new installations.[3]
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 signaling (as opposed to broadband[a]), and the 5 stands for the maximum segment length of 500 meters (1,600 ft).[4]
For its physical layer, 10BASE5 uses cable similar to RG-8/U coaxial cable but with extra braided shield. This is a stiff, 0.4-inch (10 mm)[5] 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.[6] 10BASE5 coaxial cables had a maximum length of 500 meters (1,600 ft). Up to 100 nodes could be connected to a 10BASE5 segment.[7]
Transceiver nodes 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, a hole is drilled through the outer shielding, and a spike is forced to pierce the outer three layers and contact the inner conductor while other spikes bite into the outer braided shield. Care is required 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.
Transceivers should be installed only at precise 2.5-meter intervals. This distance was chosen to not correspond to the signal's wavelength; this ensures that the reflections from multiple taps are not in phase.[8] These suitable points are marked on the cable with black bands. The cable is required to be one continuous run; T-connections are not allowed.
As is the case with most other high-speed buses, segments must be terminated at each end. For coaxial-cable-based Ethernet, each end of the cable has a 50 ohm resistor attached. Typically, this resistor is built into a male N connector and attached to the cable's end just past the last device. With termination missing, or if there is a break in the cable, the signal on the bus will be reflected, rather than dissipated when it reaches the end. This reflected signal is indistinguishable from a collision and prevents communication.
 | This section is missing information about a description of the signaling used, which is what "Physical Layer" usually means.. (May 2026) |
Stations are connected to the cable using vampire taps. This complicates adding new stations to the network because of the need to pierce the cable accurately. The cable is stiff and difficult to bend around corners. One improper connection can take down the whole network and finding the source of the trouble is difficult.[9]
This type of network was potentially more expensive to install and maintain than networks based on twisted pair cabling, since the latter might have already been present in sufficient quality as the phone network in office buildings.[10]
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Source: Wikipedia. Article content is retrieved live through the MediaWiki API.
10BASE5 (also known as thick Ethernet or thicknet) is a version of Ethernet providing 10 Mbit/s bandwidth over a thick coaxial cable having a maximum length of 500 m (1,600 ft). It was the first commercially available version of Ethernet. The technology was standardized first by Ecma International in early 1982 based on an IEEE draft standard, then by IEEE in 1983 as IEEE 802.3. Up to 100 stations can be connected to the cable in a single collision domain. The standard specifies CSMA/CD to resolve collisions. 10BASE5 was superseded by much cheaper and more convenient alternatives: first by 10BASE2 based on a thinner coaxial cable (1985), and then, once Ethernet over twisted pair was developed, by 10BASE-T (1990) and its successors 100BASE-TX and 1000BASE-T. In 2003, the IEEE 802.3 working group deprecated 10BASE5 for new installations.
Ethernet over twisted-pair technologies use twisted-pair cables for the physical layer of an Ethernet computer network. They are a subset of all Ethernet physical layers. Early Ethernet used various grades of coaxial cable, but in 1984, StarLAN showed the potential of simple unshielded twisted pair. This led to the development of 10BASE-T and its successors 100BASE-TX, 1000BASE-T, 10GBASE-T and 40GBASE-T, supporting speeds of 10 and 100 megabits per second, then 1, 10 and 40 gigabits per second respectively. Ethernet over a single twisted pair, known as single-pair Ethernet (SPE), has entered commercial use. Two new variants of 10-megabit-per-second Ethernet over a single twisted pair, known as 10BASE-T1S and 10BASE-T1L, were standardized in IEEE Std 802.3cg-2019. 10BASE-T1S has its origins in the automotive industry and may be useful in other short-distance applications where substantial electrical noise is present. 10BASE-T1L is a long-distance Ethernet, supporting connections up to 1 km in length. Both of these standards are finding applications in implementing the Internet of things. 10BASE-T1S is a direct competitor of CAN XL in the automotive space and includes a PHY-Level Collision Avoidance scheme (PLCA). The earlier standards use 8P8C modular connectors and supported cable standards range from Category 3 to Category 8. These cables typically have four pairs of wires for each connection, although early Ethernet used only two of the pairs. Unlike the earlier -T standards, the -T1 interfaces were designed to operate over a single pair of conductors and introduce the use of two new connectors referred to as IEC 63171-1 and IEC 63171-6.
Apple Attachment Unit Interface (AAUI) is a mechanical re-design by Apple of the standard Attachment Unit Interface (AUI) used to connect computer equipment to Ethernet. The AUI was popular in the era before the dominance of 10BASE-T networking that started in the early 1990s; the AAUI was an attempt to make the connector much smaller and more user friendly, though the proprietary nature of the interface was also criticized.
The Attachment Unit Interface (AUI) is a physical and logical interface defined in the IEEE 802.3 standard (additionally published in FIPS PUB 107) for 10BASE5 Ethernet and the earlier DIX standard. The physical interface consists of a 15-pin D-subminiature connector that links an Ethernet node's physical signaling to the Medium Attachment Unit (MAU), sometimes referred to as a transceiver. An AUI cable can extend up to 50 metres (160 feet), though often the MAU and data terminal equipment's (DTE) medium access controller (MAC) are directly connected, bypassing the need for a cable. In Ethernet implementations where the DTE and MAU are combined, the AUI is typically omitted. The IEEE 802.3 specification officially defines the AUI as an interconnect between a DTE and the MAU. However, devices like the DEC Digital Ethernet Local Network Interconnect (DELNI) provided hub-like functionality using AUI-compatible connectors. Additionally, under certain conditions, it was possible to directly connect two AUI devices without the need for transceivers using a crossover cable. AUI connectors became increasingly rare in the early 1990s as computers and hubs directly integrated the MAU, especially with the rising adoption of the 10BASE-T standard. This shift led to the decline of 10BASE5 (thicknet) and 10BASE2 (thinnet), which made use of the interface. The electrical AUI connection remained internally within equipment for some time. Transceivers with an AUI connector were also used by 10BASE-FL Multimode fiber. With the introduction of Fast Ethernet, the AUI interface became obsolete and was replaced by the Media Independent Interface (MII). Subsequent Ethernet standards, such as Gigabit Ethernet and 10 Gigabit Ethernet, introduced the GMII and XGMII interfaces, respectively. A 10 Gigabit Ethernet interface, known as XAUI, was developed to extend the operational distance of XGMII and reduce the number of interface signals. A smaller variant called the Apple Attachment Unit Interface (AAUI) was introduced on Apple Macintosh computers in 1991, and was phased out by 1998.
Before the 1921 destruction of Tulsa’s Greenwood District, Black residents had created a remarkable center of business and community life. The district included stores, professional offices, entertainment venues and homes owned by Black citizens. Understanding Greenwood means learning what was built—not only what was burned.
MORE →The Greenwood District.
