This project is based on my original schematic from the year 2005, when I also built and tested a perfboard prototype. I didn’t think much of it then, but, at least on the Internet, it has since become an exemplary circuit for the “passive Ethernet hub” in general. I’ve seen it featured in the prior art sections of patent applications, etc.

Especially now, in 2026, Ethernet hubs are hardly ever needed in practice. Some niche applications may exist, though. In any case, it makes for an interesting experiment and a demonstration piece.

The Ethernet signal is heavily attenuated by the hub, but 10BASE-T is significantly more robust than 100BASE-T, because 10BASE-T uses only two nominal voltage levels, has a larger noise margin, and occupies a lower and narrower range in the frequency domain. I tested the prototype with three PCs that were connected to the hub with 10, 16, and 22-meter-long Cat5 cables. The usual small office tasks – remote folder browsing, moving documents and spreadsheets around – worked as expected at 10 Mbps, without any major delays. Even when one of the computers was 35 meters away, it worked adequately.

This hub doesn’t require power to operate. It can be used in telemetry or remote control applications where little data is transferred, while having one less thing to power is a critical advantage.

The schematic calls for 24 diodes. In this version there are 12 pieces of BAV99 dual diodes (D1-D12) in SOT-23 cases. I measured the forward voltage drop of each diode as 0.72 V at 10 mA and 0.77 V at 25 mA.

For the connector type, please see the very short Bill of Materials.

Someone on YouTube was kind enough to build this hub in a college lab, to examine it properly and confirm that it works:

https://www.youtube.com/watch?v=FkHuOrr_WNk