Rotary Phone Museum Exhibit

dial-telephone-museum-exhibit[David Burroughs] wrote in to share this dial telephone museum exhibit he built and we’re glad he did because we love interactive museum hacks. He mentions that it’s not really tied to the theme of the Roads and Rails Museum in which it’s installed. But when we think of railroad history we also think of telegraph. And that’s just a hop, skip, and a jump from telephones.

The display allows museum goers to play with the rotary dial on the phone. The box next two it contains a 10-position relay increment switch. So each pulse from the dial increments the switch. There’s a satisfying click, a moving arm, and different colored LEDs which highlight the inner workings. An Arduino board monitors the phone, displaying the dialed number on a seven segment display then incrementing the relay.

We figure the interesting part is to see that telephony used to use mechanical switching like this. But the video below includes a story about the kid who asked how you carried this phone around. This brings to mind the phrase “hang up the phone”, which doesn’t have the same literal meaning it used to.

40 thoughts on “Rotary Phone Museum Exhibit

      1. I think it detracts from the display, because it makes the viewer think you -need- a microprocessor to count the clicks before anything happens.

        Which is exactly how it didn’t work.

        1. I agree: I seem to recall seeing an article here many years ago that showed how the old rotary switches worked based on the clicks from the dialing phone, and I remember the awe that it instilled to watch the massive switches clicking away. I was somewhat disappointed when I read above that the arduino is driving the switch. :-(

        2. Ditto – The arduino is a distraction. Telephone systems worked fine for 70 years without any processor involvement. The dial pulse-count should be used to directly drive the ‘item’ – otherwise known as a uniselector.
          Otherwise I appreciate the sentiment and idea of the project – just that it should be done ‘properly’ to illustrate the methods used.
          Using the same pulse-dial phone into simple relay logic – to reset the uniselector – and let the actual mechanism count the dial pulses.,
          If a LED display is really necessary, a simple ‘decimal to seven-segment’ decoder could be implemented to display the actual uniselector position (which is more relevant – as it shows the result rather than the ‘expected’ position… ever dialled a wrong number anyone?!

  1. I briefly worked for the telecom department at Burlingtin Northern, and yes telephones were a big deal. Telegraph went out in the 1970s bit voice was a big deal probably starting after WWII. At the time BNet was the world’s second largest private telecom network (they owned the wire and fiber, the right of way and microwave towers. Huge!

    Also sprint was a big part of SP railroad before they went independent.

    Telecom was a huge part of railroading .

    1. I wouldn’t be surprised if a lot of the newer equipment they’re rolling out to new housing developments doesn’t support pulse dialing. However, a microcontroller could translate the pulses to DTMF tones, which would work with modern systems! (It might have to buffer entire phone numbers and spit them out like speed dial though, depending on how long a delay the phone system will wait for between digits.)

      This could also be adapted to make a PC VOIP phone, maybe assigning 7-digit macros to each of your Skype contacts or something like that. You’ll be dialing KL5-3226 and PE6-5000 again in no time!

    1. Yes but only if you know about it! I’m reminded of my friend as a teenager, who’s dad ingeniously unscrewed his phone and removed all the number buttons (except 9, with 999 being the emergency services). I taught him manual pulse-dialling, though there was the second, lower-tech option of just sticking a pen into the holes, the rubber pad was still there!

    1. Yup. The paper sign next to it mentions something about the microprocessor driving the display. In the good ol’ days, there wasn’t a microchip in the world, never mind a telephone exchange! Kids don’t need informing how he built his hack, that’s for geeks to appreciate and kinda spoils the educational value.

      Beside that, I’ve just noticed he’s taken the damn handset off! How are you supposed to use a phone like that!?

      It’s a shame cos getting hold of the uniselector is pretty good luck, shame he didn’t try to make a more authentic setup. And where’s the handset!?

    2. It really is unattractive. It looks unprofessional. I worked a museum and that wouldn’t of ever been allowed. But, the thought was there. It just needs cleaned up.

  2. 7447 driven by 7490, anyone?

    Also, in response to some of the first comments, it would have been cool in the past if they had made a huge rotary dial that included the alphabet, and somehow mechanically output morse code….

  3. Awesome! I think having the uniselector more visible would be good though, have it laying out on a little desk, with a clear cover so kids can see it from all sides ticking away. Put it on top of a model “exchange” building, to make it clear it isn’t something you have in the home. You could even go as far as tiny telegraph poles.

    Have several telephones connected to it, just using a 1-digit phone number. so a kid could dial a number and talk to his friend on one of the other phones. 4 or 5 phones would be nice, and the kids take turns being able to dial. I suppose it’d be easiest to only have one “master” phone do the dialling, since the other bits of an exchange aren’t there.

    The extra electronics for generating ringing etc, could be snuck away in a little box and done with modern hardware. The visible hardware would still make the point. There’s plenty of circuits about for ringing phones, theatres sometimes used them to ring a phone in a play.

    It would be good, if possible to use different coloured phones, or at least a coloured sticker on each phone. Then each phone could have a same-coloured wire connected to the uniselector, to make it obvious how they’re all connected up.

    Anyway I’m getting carried away… but it is wierd to think that kids today, even teens, have had cellphones around their whole life. And the Internet come to think of it. And I’m not even really old!

    1. “Anyway I’m getting carried away… but it is wierd to think that kids today, even teens, have had cellphones around their whole life. And the Internet come to think of it. And I’m not even really old!”

      Especially when you think about all the location tracking stuff the NSA/FBI/etc are doing with mobile phones, and internet surveillance to boot. It seems like an akward time for them to know nothing else.

    2. The Museum of Science and Technology in Ottawa, Canada has something like this–an operator’s panel with several hand-cranked phones connected (no automatic switching equipment, although they have some in storage). I saw a family calling each other with help from an employee, who even showed them how the operator could spy on people.

  4. This brings to mind the phrase “hang up the phone”, which doesn’t have the same literal meaning it used to.

    Very little of the terminology of telephony has kept up with the technology. “Dialing” a phone would require an acutal dial, which is a disk with a rotational aspect, and a DTMF keypad or cell phone has neither. “Ringing” is the sound of an electromechanical bell, but actual bells haven’t been used for a long time either. “On hook” and “off hook”, related to hanging up a phone, mean nothing to a device with no hook. The icon for a recorded message remains a pair of reel-to-reel tape reels, yet answering machines haven’t been built with actual tape recorders for a long time. “Tip” and “ring” are still the names of the green and red wires, but they’ve meant nothing since the days of operators and switchboards. For that matter, an “operator” hasn’t operated a phone system since the switchboards were phased out.

    1. Too right. The technology was low tech and designed for reliability, which is exactly what you want in a service you use to call the fire or police. Those of us who have been through blizzards and hurricanes know just how useless cell phones are in a real emergency — if the cell site isn’t overloaded by folks calling their family and friends to check on them, the generator has run out of propane or diesel. With landlines, if a tree hasn’t landed on them, you can still call the emergency services.

    2. “some day we’re gonna wish we hadn’t done away with our landlines…”

      I still use land lines and have never owned a cell phone. During hurricane Charlie here in Florida the cell phone service was down for about 4 days in our area (towers blew away) and people in the ‘hood would line up at my door to use my land line. I had buried lines. My house became a community phone booth. Also people had no electrical power to charge their phones or gasoline to drive their cars. It was like an apocalypse movie.

      By the way, what ever happened to phone booths? What does Superman use now?

      1. Amazing how helpless some people are when their cell phone is on the fritz. I just downgraded to a non-smart (or, as I like to think of it, a “smarter” phone) cell phone… just wasn’t using the data, turns out I didn’t actually *need* it (go figure). Went through Ting, pay less than $20 per month. Good for occasional calls/texts and to have for emergency purposes… not much of a point otherwise. If someone really needs to talk to me, they can call the house phone and leave a message and I’ll get back to them when I get back to them.

        There’s nothing actually urgent going on… that’s the kicker. Folks try to insist that they have to stay glued to their cell phone because everything’s too important to wait. I find that quite amusing. Unless you’re a surgeon who’d on-call, or you’ve got a relative/friend literally on their deathbed, everything else can wait.

        Ask what would happen if you didn’t take that “urgent” call. Be honest about it. Drill down about what each consequence would mean/result in. If you’re completely honest, you soon realize that the false sense of urgency that has been drummed into our collective consciousness is complete nonesense… it’s largely advertising, propganda/control, and enterainment addiction.

        Step back. Turn the cell phone off. Breathe. Reflect. Make something with your hands. Slow Down. You’ll be happier, healthier, and better off for having done so.

        1. I remember in the old days of the 80s and early 90s, if you arranged to meet someone you had to be there, exactly the right place and time, or the meeting fails, one or both of you waste time hanging around, and your plans for the day are spoiled.

          Mobile phones do away with that. You don’t even have to make the plans anymore! Just phone your friend when you’re in town, or wherever, ask where they are and meet up straight away. If you’re delayed or get lost, you can tell them instantly. That’s one minor pain in the arse I’m glad to see go.

          For “important” people, there’s been radio pagers since what, the 1940s? I think it was the 1970s when they became addressable on a large scale, so thousands could share a frequency, and only beep when their address code was sent out. Prior to that the best they had was using up frequencies, and I think sometimes using a small tuning fork / reed to pick up a modulated audio tone.

          I like to have my phone on me now. People expect it of you. But why not? It’s easier than chasing around messages. You want to talk to someone, you just pick their name from a list, it’s like telepathy! Everyone’s mind and opinion is available, instantly.

    1. I grew up with only rotary phones in our house, but some of my friends had never seen one before. Heck, I remember when push button phones used to need a switch on them to change between pulse and tone. Use pulse to dial, then switch to tone if there was an automated answereing system. I have a cell phone, but I can’t get a hardline, everything by me is VOIP only. Unless you pay, you can’t even dial 911 (emergency services).

    1. my grandmother was still on a party line in Northern NJ (not at all rural now) up til she passed away in 2010. Of course, she was the only party on the party line (for 30 years or so, at least), but that was still how it was configured at the phone switch and that was still how it was being billed. Was a darn sight cheaper than any of the “normal” landline billing options that were available to anyone in that neighborhood requesting new service.

      1. Ironically now, if you want a “party line” where you can talk to a bunch of strangers, you can call a premium-rate number for all the fun of doing it!

        Actually you don’t see them advertised as much as you used to. Suppose the Internet’s to thank for that. Mostly when you see ads it’s just straightforward sex lines.

        I wonder, does that mean it would be free for your gran to talk to her co-partying neighbours? Just jiggle the hook a bit to make them ring, then pick it up? And either ignore the dialtone, or wait for it to switch off? Just sounds like a handy advantage to a system that otherwise sucks in many ways.

  5. Wow that picture brings back memories, and makes me feel very old. My parents had that exact phone model for many, many years. Even back then many people couldn’t figure out how to use it (late ’80’s). I can still hear that distinctive rotary phone sound…

  6. Random recollections:

    * IIRC, dial pulses would *open* the loop current

    * As a kid, I once experienced the din and ozone of a step-by-step office in action. The clatter of thousands of Strowger switches was enormous, omnipresent, yet one was hard-pressed to see any one switch in sight move move. There racks were tall (or maybe I was shorter) in those days. Carts full of lengths of wire for maintenance.

    * A great book on the ‘crossbar switch’ and its electro-mechanical ‘common control’, successor to the Strowger switch, was David Talley’s “Basic Telephone Switching Systems”

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