At the Connections Museum: the insane telephone technology that led to today's computers

same. And it remains connected by some kind of miracle. And as long as you keep this magnet vertical, this cross point will stay connected. So the selected magnet can be released, but the vertical magnet will actually maintain that connection as long as it is in operation. And what's happening here is that these selected magnets have little fingers of wire sticking out of them in that crossbar switch array. And that cable can go up or down. And when that wire goes up or down, it interferes with that vertical magnet. And when that vertical comes in to close the connection, it pushes that wire in, which then causes these contacts here to actually close.

But if you look at these contacts right here, right where my finger is. And I go horizontal, sorry, horizontal and vertical. You can see them getting closer there. Yes we look at it. I mean, the genius of that thing is that it doesn't block. Exactly. You can have any or all contacts on or off at the same time. All positions are valid, there is no waiting for something to be available or not. All of them are available to you at all times. Good. And the control element of this, called a dialer, which I'll show you, can observe the state of the entire switching network at the same time.

And then make a decision about how to route that call or how to connect it. And if the first route is not available, you can try again and again. And also very scalable, because it is a normal left and right array. In fact, they initially created memories of that for the broadcast

computers

, because it's very scalable. And if you've seen my video about the Japanese FACOM 129B relay computer, you'll have recognized the devices they used to make its 23,000-bit memory. Yes, the RAM in this computer is made of these same crossbar elements. The hardest part is connecting the 600 cables, you know, for the next thing.

But if you want to make it bigger, you can basically put in a new frame. So, very scalable. It's very, very scalable. I hear the noise, but I don't see anything. Search here. You'll see it eventually. Yes. It's also much faster than the panel, because you don't have to scroll. Like the other machine, this is also a set of test equipment, but is it even better? It's even better. One of the ways they did it is with this problem logger, which actually prints a physical log every time this machine encounters a fault. So I can simulate it for you.

Okay, then look here. Okay, I'm looking! Oh! It's a punch card. And the holes in the card are a kind of stack trace. And then we can take these cards and by looking at the holes in them, we can see... ...figure out what the problem is. Yeah! Small holes! Perforated card! Well, it's no small thing, it's a big punch card. Great punch card! Well, we'll have to overlook other marvels of machinery, including the calculating call timer clock and the automatic call billing punching machine, so we can rejoin the electronic age, with the 3ESS computerized switch, courtesy of Bell Labs.

So now we're taking a giant leap into the future, we're in 1970 something, five, six? 1976. 1976. And it has been computerized. And this is? Number 3ESS. Yes, 3ESS. So when I went to Bell Labs, I arrived on the scene when they were at 5ESS, and it was a big deal. So we'll just apply 48 volts to everything. Ah, 48 volts, of course. Oh, I heard I heard relays. Good. All the relays work and now there are a bunch of power converters on the other side that we have to turn on. It's OK, go ahead. (fans start whirring) And these are several peripherals that the computer will want to use, once it starts coming to life.

And we'll turn on this computer. You need to turn the switch on the back. I'm going to turn on the other computer. So this is a pair of redundant

computers

. It will take several minutes to read that tape drive. But as you can see, it's kind of an indication of progress, just to say that it's doing something. I was asking if it was typical 70's

technology

, TTL. And the answer is yes and no. There are some things that look like they've gone to the Moon, which are ceramic chips. The heyday of Bell Labs, when they could do whatever they wanted.

You can also see why Linux (UNIX) came from Bell Labs, because they needed a computer that was A) secure and B) that ran 24 hours a day. It didn't need to be rebooted, it could recover from a failure. Even though this system doesn't run Unix, the software development problems, the hassles that went into doing it, was one of the big inspirations for Bell Labs to say, okay, we need to have an operating system that can't just be an operating system for these machines, but also a development platform for the software that will be nice. So in truth, switch computers influenced Unix.

Absolutely. What would be the terminal that would be there? A ticker. This boy here. Oh, an ASR 33? A 35 is what the original would use. And ours is in storage and we haven't made the trip to the warehouse to return it. Yes, the 35 would be the much more robust version of the 33. That's it! Is running! That's all? That's all! I hear a click click. Are they the seconds? Yes. Oh yes. Oh, and it tells you very, very slowly, at any speed. 110 baud exactly.. It cries out for a mechanical terminal. How many of those still exist? These machines?

Yes. Zero! Is everything gone? This is like our dashboard. We're pretty sure this is the only preserved example. Wow. So that you do not end a line with the Enter key. You end a line with bang. And then he tells you immediately: Follow the impression. Which means it is working and will eventually get back to you. Very concise. Very, very concise, again because, ticker. Teletype, right. Yes, you can't talk on teletype. Correct, UC diagnosis complete, all tests pass. You have to do your short hand pretty well! Yes, yes, you do. AHA! And now we understand that this is normal light!

Is working! Did you understand it? That's what we like to see. Oh very well! So now we should be able to make a call. This is how we do it... Here we go. Alright! We got it, go ahead, Peter. Hello? Hello! Oh yeah, I think Marc is here. Let me see if I can get it for you. Thank you. (laughs) We use this little machine to make a phone call! Amazing! So the next time you use a computer, take a minute to thank the

telephone

, Bell Labs and its invention of the transistor, and Unix and its derivatives.

And don't forget, if you're in Seattle on Sundays, there's a gem of a

museum

waiting for you to visit. See you in the next episode!