HP EtherTwist Hub/8: A Look Back at Early Twisted-Pair Ethernet
The HP 28691A, better known as the HP EtherTwist Hub/8, is a compact Ethernet hub from the early 1990s. Although it may look simple compared with modern network equipment, it represents an important stage in the development of local-area networking.
The device comes from a period when Ethernet networks were gradually moving away from coaxial cabling and adopting twisted-pair connections. The familiar RJ-45 Ethernet port was becoming increasingly common, but many offices still depended on older coaxial network segments. Equipment such as the EtherTwist Hub/8 helped connect these two worlds.
Eight Ports of 10BASE-T Ethernet
The front of the HP EtherTwist Hub/8 contains eight RJ-45 ports designed for 10BASE-T Ethernet. Each connected computer communicates at a maximum theoretical speed of 10 Mbps.
Today, even basic home network equipment commonly supports 1 Gbps or more. However, 10 Mbps was entirely suitable for many office applications of the period, including file sharing, network printing, electronic mail and access to centralized business systems.
The important detail is that the HP 28691A is a hub, not a switch.
A modern Ethernet switch learns which device is connected to each port and sends traffic only where it needs to go. A hub works more like an electrical repeater. When a signal enters one port, it is repeated to all the other ports.
As a result, every connected computer shares the same available bandwidth.
Shared Bandwidth and Ethernet Collisions
Because all ports belong to the same shared network segment, the hub operates as a single collision domain. If two computers attempt to transmit at exactly the same time, their signals may interfere with one another.
This creates an Ethernet collision.
Early Ethernet networks handled this through a mechanism known as CSMA/CD—Carrier Sense Multiple Access with Collision Detection. Before transmitting, a computer listens to check whether the network is already in use. If a collision still occurs, the computers stop transmitting, wait for a short random period and then try again.
The EtherTwist Hub/8 therefore operates in half-duplex mode. A device can transmit or receive at a given moment, but it cannot perform both operations simultaneously in the way modern full-duplex Ethernet equipment can.
This shared behaviour makes the hub particularly interesting for demonstrations. When several computers exchange data through it, the activity indicators provide a visible representation of how traffic is repeated across the network.
Connecting Twisted-Pair and Coaxial Ethernet
One of the most historically interesting features of the HP 28691A is its BNC ThinLAN connection.
This interface was intended for 10BASE2, also known as Thin Ethernet or ThinLAN. Instead of connecting every computer to a central hub, 10BASE2 systems used a length of RG-58 coaxial cable running between the computers.
Each computer was attached through a BNC T-connector, and the complete cable segment had to be terminated with a 50-ohm terminator at both ends. Missing terminators, loose connectors or damaged cabling could cause the entire network segment to become unreliable.
By including both RJ-45 and BNC connectivity, the EtherTwist Hub/8 could act as a bridge between generations of physical network infrastructure. Newer computers could connect through twisted-pair cabling, while an existing coaxial segment could remain in service.
This was especially useful for companies that wanted to modernize their networks gradually rather than replace all of their cabling at once.
Using the HP 28691A Today
The EtherTwist Hub/8 can still be used, although connecting it to modern equipment may require some planning.
Not every current network adapter supports 10 Mbps operation, and some modern devices may not correctly negotiate a half-duplex connection. One practical solution is to place an older 10/100 Mbps Ethernet switch between the HP hub and a modern network.
Older computers with 10BASE-T or 10/100 Ethernet adapters are usually the most suitable devices for demonstrations.
The BNC connection requires additional components:
- RG-58 coaxial cable
- BNC T-connectors
- Two 50-ohm terminators
- Network adapters with native 10BASE2 support
The coaxial network must be assembled as a continuous bus. The cable cannot simply be connected directly from the hub to a computer without the correct T-connectors and termination.
A Useful Museum Demonstration
For a technology museum such as 8BitClub, the HP EtherTwist Hub/8 can be used to demonstrate several important networking concepts.
A display could include two or three period-correct computers connected through the RJ-45 ports. Visitors could observe file transfers, shared network resources or multiplayer games running over a genuine 10 Mbps hub-based network.
A second group of computers could be connected through a 10BASE2 coaxial segment. This would make it possible to compare bus and star topologies in a working installation.
The hub could also be used with packet-analysis software to show that traffic is repeated across every port. Unlike a switched network, a computer connected to a hub can observe much more of the traffic generated by other machines on the same segment.
This makes the device useful not only as a historical exhibit, but also as an educational tool for explaining Ethernet operation.
From Shared Ethernet to Modern Networks
The HP EtherTwist Hub/8 represents a transitional period in networking history.
It combines the older shared-medium philosophy of Ethernet with the physical star topology that later became standard. The cabling resembles a modern Ethernet installation, but the electrical and logical behaviour is much closer to the original coaxial Ethernet networks.
Modern switches have eliminated most of the limitations associated with hubs. Every switch port can operate as an independent connection, devices can communicate in full-duplex mode and collisions have effectively disappeared from ordinary Ethernet networks.
Speeds have also increased dramatically—from 10 Mbps to 100 Mbps, 1 Gbps, 10 Gbps and beyond.
Despite these advances, devices such as the HP 28691A remain important. They show that the development of networking was gradual, with equipment designed to maintain compatibility while organizations moved from one standard to another.
The HP EtherTwist Hub/8 is therefore more than an obsolete networking box. It is a physical reminder of the period when twisted-pair Ethernet was still new, coaxial networks were still common and a 10 Mbps shared connection was enough to connect an entire office.
At 8BitClub, it can help bring that history back to life.
