Strowger Telephone Switch (1891) (en.wikipedia.org)

A few percent error rate, but no single point of failure.

I went to a telephone maintenance school in the Navy in Virginia, 1976. We studied these things, but I never encountered one in the wild.

Great video about it. https://www.youtube.com/watch?v=xZePwin92cI

The museum of science and technology in Ottawa had a working demo of a stepper switch. When you hear one in action you quickly realize how a rotary telephone works and why it makes the noise it does.

I've heard people say it's quick the sound to hear a CO full of them in action.

There's an art project from a few years ago which made a feature of running Strowger switches. The art aspect deals with migration and conflict minerals.

http://yoha.co.uk/tantalum

"The first thing that visitors see is a towering rack consisting of electromagnetic Strowger telephony switches. The undertaker Almon Brown Strowger patented this design in 1891, the first automated telephone system of its kind. The switches are triggered by a computer..."

cstross is fond of a tale that the Mexico City telephone exchange continued working from underneath an earthquake-collapsed building, because it was running on Strowger switches. I haven't been able to track down a reference elsewhere, though.

Until the mid 80's MIT Dormline ran on a Strowger switch. It was replaced by a 5ESS dedicated to, and IIRC, owned by MIT.

I have seen Strowger switches in the wild.

In 1965-66, my first grade class visited the local AT&T Central Office. We saw a wall of what I later identified as Strowgers. I thought they looked like mailboxes on end at the time.

The MIT dorm phone system used Strowgers at least through 1980, and could be seen by curious students.

Still the best way to explain net neutrality to a layman.

My dad was a telephone engineer in the 80s and 90s in the UK. He took me to the exchange a few times and I can still recall the impressive noise of the Strowger (or maybe they were Director) units.

My dad was a telephone engineer in the 80s and 90s in the UK. He took me to the exchange a few times and I can still recall the impressive noise of the Strowger (or maybe they were Director) units.

"He was said to be convinced that she, as one of the manual telephone exchange operators, was sending calls "to the undertaker" to her husband."

Wonderful tidbit.