The Ethernet standard introduced in 1990 was 10BASE-T, formally published as IEEE 802.3i on September 28, 1990. It ran at 10 megabits per second over ordinary unshielded twisted-pair copper wiring, the same type of cable already used for telephone lines. This was a major departure from the coaxial cable designs that came before it, and it became the version of Ethernet that brought networking out of specialized labs and into mainstream offices.
What 10BASE-T Actually Changed
Before 10BASE-T, Ethernet relied on coaxial cable. The original 1983 standard, 10BASE-5 (often called “Thicknet”), used a thick, rigid coaxial cable that required physically drilling into the wire to make a connection. Its successor, 10BASE-2 (“Thinnet”), switched to a thinner, more flexible coax connected with twist-on BNC connectors, but it still had a fundamental problem: every device on the network shared a single run of cable. If one connection failed or someone accidentally disconnected a segment, the entire network went down.
10BASE-T solved this by using a star topology. Instead of daisy-chaining devices along one cable, each computer connected individually to a central hub using its own twisted-pair cable with an RJ-45 connector, the wider cousin of a standard phone jack. A fault in one cable only affected that single connection, not the whole network. And adding a new device was as simple as plugging another cable into the hub, with no interruption to anyone else.
Cabling and Distance Limits
10BASE-T required Category 3 (or higher) unshielded twisted-pair cable with a maximum segment length of 100 meters, or about 328 feet. That was shorter than what coaxial Ethernet allowed: Thinnet supported 185-meter segments, and Thicknet could stretch to 500 meters. But the tradeoff was worth it. Twisted-pair cable was cheap, thin, flexible, and already installed in many buildings for phone service. Running new cable was far easier and less expensive than routing rigid coax through walls and ceilings.
A single 10BASE-T network could include up to five segments and support up to 1,024 devices per segment, though real-world deployments were typically much smaller. The standard supported up to four “hops” between segments, meaning you could link hubs together to extend the network across a building or campus.
Technology Behind the Standard
10BASE-T used Manchester encoding to transmit data at 10 megabits per second. This encoding method embeds a clock signal directly into the data stream by introducing a voltage transition in the middle of every bit. The receiving device uses those transitions to stay perfectly synchronized with the sender, which makes the connection reliable even over inexpensive, unshielded cable. Manchester encoding had already proven itself in earlier Ethernet versions and in applications ranging from spacecraft communications to floppy disks.
One small but important addition in 10BASE-T was a feature called “link beat,” a periodic pulse sent over the cable even when no data was being transmitted. This let devices and hubs immediately detect whether a cable was properly connected, a convenience that earlier coaxial standards lacked.
What Came Before 10BASE-T
10BASE-T didn’t appear out of nowhere. Two earlier products explored the idea of running Ethernet-speed networking over twisted-pair cable. StarLAN, standardized in 1986 as IEEE 802.3e, proved the concept but only ran at 1 megabit per second. LattisNet, developed by SynOptics in January 1987, reached 10 megabits per second but used a different signaling method and wasn’t compatible with standard Ethernet equipment.
In 1988, AT&T released StarLAN 10, an upgraded version running at 10 Mbit/s. Its signaling approach became the foundation for 10BASE-T, with the addition of link beat for connection status monitoring. The IEEE formalized all of this into the 802.3i standard, giving the industry a single, interoperable specification that any manufacturer could build to.
Why 10BASE-T Mattered Long-Term
The shift to twisted pair and star topology didn’t just make Ethernet cheaper and more reliable. It created the physical infrastructure that every faster generation of Ethernet would build on. When 100 Mbit/s Fast Ethernet arrived a few years later, it used the same RJ-45 connectors and the same star wiring layout, just with higher-grade cable. Gigabit Ethernet and even 10-Gigabit Ethernet followed the same pattern. The basic networking design that offices and homes still use today, with individual cables running from each device to a central switch, traces directly back to the choices made in the 10BASE-T standard.
As IEEE put it, before 10BASE-T, Ethernet was “a complex of snaking cables in ceilings.” After it, networking became something any building could support with standard wiring and off-the-shelf hardware.