In early Ethernet networks, vampire taps were used to connect devices to a single coaxial cable.

You could add a new device in between physically - without disrupting existing connections.

Here's an actual video of a connector bring made:

https://youtu.be/ehCwqMkAxq0

see also: https://news.ycombinator.com/item?id=24807542

I'm glad a lot of people have done this and have commented on this and it's a decade ago.

I hope more people get to try this out when they can. Ethernet is a bus, and after switching, the usage has become point to point. It will be a fun experience to get.