Lucent 7 R/E 5ESS Telephone Switch Rescue (2024)

I wonder how many operating 5ESS are left now.

Talk about a gargantuan project.. also awesome to bag such a thing. He's lucky to even have the resources to store^W warehouse it

Visiting Bletchley Park and seeing step-by-step telephone switching equipment repurposed for computing re-enforced my appreciation for the brilliance of the telecommunication systems we created in the past 150 years. Packet switching was inevitable and IP everything makes sense in today's world, but something was lost in that transition too. I am glad to see that enthusiasts with the will and means are working to preserve some of that history. -Posted from SC2025-

(2024), but still a good read!

Author and surprised to see this here but happy to see interest in these historical machines.

I will also plug Connections Museum who have an already neat installation in Seattle and are working on their own 5ESS recovery for display at a new site in Colorado https://www.youtube.com/watch?v=3X3-xeuGI5o

My first development job was as a software developer at Bell Labs in Naperville working on the 5E. I started at the end of 5E4 (the 4th revision) and then worked on 5E5 and 5E6. I went from school writing maybe 1000 line programs to maintaining and enhancing a system comprised of millions of lines of code and hundreds of developers. Most of the code itself was very simple but it was the interactions between modules and switching features that was very complex.

> In particular, the machine had an uptime of approximately 35 years including two significant retrofits to newer technology culminating in the current Lucent-dressed 7 R/E configuration...

Pretty impressive. It makes me sad that the trend is to move away from rock-solid stuff towards more and more unreliable and unpredictable stuff (e.g. LLMs that need constant human monitoring because they mess up so much).

This is such a stark contrast with how "critical infrastructure" is built now.

A university bought a 5ESS in the 80s, ran it for ~35 years, did two major retrofits, and it just kept going. One physical system, understandable by humans with schematics, that degrades gracefully and can be literally moved with trucks and patience. The whole thing is engineered around physical constraints: -48V, cable management, alarm loops, test circuits, rings. You can walk it, trace it, power it.

Modern telco / "UC" is the opposite: logical sprawl over other people's hardware, opaque vendor blobs, licensing servers, soft switches that are really just big Java apps hoping the underlying cloud doesn't get "optimized" out from under them. When the vendor loses interest, the product dies no matter how many 9s it had last quarter.

The irony is that the 5ESS looks overbuilt until you realize its total lifecycle cost was probably lower than three generations of forklifted VoIP, PBX, and UC migrations, plus all the consulting. Bell Labs treated switching as a capital asset with a 30-year horizon. The industry now treats it as a revenue stream with a 3-year sales quota.

Preserving something like this isn't just nostalgia, it's preserving an existence proof: telephony at planetary scale was solved with understandable, serviceable systems that could run for decades. That design philosophy has mostly vanished from commercial practice, but it's still incredibly relevant if you care about building anything that's supposed to outlive the current funding cycle.