Typewriters, Cash Registers, and Calculators

September 20, 2018 12:43 AM

Picture the keypad of a telephone and calculator side by side. Can you see the subtle difference between the two without resorting to your smartphone? Don’t worry if you can’t recall the design. Most of us are so used to accepting the common interfaces that we tend to overlook the calculator’s inverted key sequence.
posted by eotvos (24 comments total)

Benfords’s Law
posted by fallingbadgers at 1:06 AM on September 20, 2018 [1 favorite]

"A calculator has the 7–8–9 buttons at the top whereas a phone uses the 1–2–3 format."

Oh really now?

Every single phone I ever encountered in Denmark (except this) were numbers running left to right, bottom to top.
posted by Dysk at 2:02 AM on September 20, 2018

I have a vivid memory of being in my early teens in school, and for whatever reason, the teacher asking me to phone somebody. I had the number written down on a scrap of paper, and I had the phone in front of me, and to my confusion I ended up misdialling the number not once, not twice, but three times in a row.

For someone so used to the keyboard number pad and calculators, and not a big telephone user, I couldn't break the muscle memory of '1 2 3' at the bottom and '7 8 9' on top. Even when I realised what was happening, I still would hit a 1 instead of 7.
posted by Gordafarin at 2:30 AM on September 20, 2018

There’s no logical reason why telephones and calculators use different numeric keypads.

Perhaps I'm just rationalizing, but since calculators will typically be used for actual quantities (which have a strong bias towards starting with lower digits) it makes sense to put them at the bottom where they are close to the arithmetic operators and equals buttons so your finger doesn't need to move as far. OTOH, phone numbers are not quantities, they are just arbitrary identifiers so won't follow Benford's Law, and in that case it's more intuitive to put them in conventional top-to-bottom left-to-right order. The fact that most people don't notice and can't recall the difference is evidence that it is intuitive (or at least becomes second nature after a while).
posted by L.P. Hatecraft at 2:36 AM on September 20, 2018 [11 favorites]

There have been two related posts about keypad design previously on the blue: Dial D for Design and A calculated design.
posted by James Scott-Brown at 3:46 AM on September 20, 2018 [3 favorites]

OTOH, phone numbers are not quantities, they are just arbitrary identifiers so won't follow Benford's Law

In the olden days of dials and pulses, they were quantities, which is why the area codes in the most populated areas are biased toward low numbers (not counting 0, which required ten pulses rather than none).
posted by Etrigan at 3:47 AM on September 20, 2018 [7 favorites]

I pranked a coworker at a previous job by disassembling his desk phone and rearranging the number caps to calculator layout. He spent all afternoon trying to figure out why he couldn't dial out.
posted by backseatpilot at 5:16 AM on September 20, 2018 [12 favorites]

Some banks have a telephone-like keypad on their ATMs but provide a calculator-like keypad when the teller asks you to set your PIN. If you assume that the teller's device is laid out like the ATM, you'll write down the wrong PIN, go to test it at the ATM, and immediately return having apparently forgotten your PIN in the minute it takes to walk back out to the lobby. It will take multiple tries to convince yourself and then multiple more to convince the teller that something's really wrong.

I speak, of course, purely hypothetically.
posted by meaty shoe puppet at 5:32 AM on September 20, 2018 [15 favorites]

That article raised an even more interesting question for me. Why did so many early calculators and adding machines lack a key for zero? How could you even use them.
posted by TedW at 5:42 AM on September 20, 2018 [2 favorites]

I don't even remember when I last used a phone keypad. It's 2018, if you're calling a number that's not already saved in your phone, chances are you found it on the internet so you can just copy & paste it.

In fact, I just opened the caller app on my phone and it took me a few confusing seconds to even figure out how to show the keypad.
posted by Vesihiisi at 6:08 AM on September 20, 2018

At jobs that involved heavy use of both a desk phone and 10-key, I had to keep the phone on my left so that I always dialed the phone with my left hand, and typed on the keypad with my right. It's the only way that works for me.

Now I've got a VOIP phone at work and can just copy and paste phone numbers, no physical dialing required. Whew.
posted by asperity at 6:09 AM on September 20, 2018 [4 favorites]

Way back in the early 90s I did data entry on Nixdorf terminals whose embedded 10-key was phone style, not calculator style, like this. A few years later they started switching over to more traditional PCs, but they had to jump through a few hoops to keep the 10-key the way it was, because you do not screw with your fastest typers by inverting their numpads.

It took me a while to get used to normal 10-key work in later jobs, to be honest.
posted by Kyol at 6:37 AM on September 20, 2018 [1 favorite]

I make a distinction between casual/occasional number entry and long/heavy number grinding. In the first category any logical sequence or arrangement will do. Think of a rotary dial telephone or the numbers across the top a keyboard. In the second, it becomes muscle memory and ergometrics. Plant your hand in one place and grind, sometimes for hours. That the inverted sequence became standard is probably irrelevant...
posted by jim in austin at 6:43 AM on September 20, 2018

Some banks have a telephone-like keypad on their ATMs but provide a calculator-like keypad when the teller asks you to set your PIN.

I always set my PIN by the shape it makes on the keypad, and this has screwed me up repeatedly when I need to interact with one of the bank's desktop computers.
posted by Rock Steady at 7:02 AM on September 20, 2018 [1 favorite]

Researching this topic led me to this video of a mechanical calculator encountering a divide by zero error.
posted by SPrintF at 7:50 AM on September 20, 2018 [3 favorites]

Why did so many early calculators and adding machines lack a key for zero? How could you even use them.

Adding machines had the keys already in the unit positions, so for 10 you'd just enter the 1 in the tens position. Doing nothing in the ones position is the same as entering the trailing 0.

There used to be little handheld mechanical calculators that worked similarly. Here we go.
posted by ChurchHatesTucker at 8:48 AM on September 20, 2018 [2 favorites]

In the olden days of dials and pulses, they were quantities

And for anyone who's curious, this is what all those pulses were doing.
posted by Mr. Bad Example at 9:26 AM on September 20, 2018 [4 favorites]

AKA why I'm 15 seconds late to every GoToMeeting.
posted by kevinbelt at 10:25 AM on September 20, 2018 [2 favorites]

Yeah, my grandfather and mother were bankers in the 60s-70s. My grandparents always had an "adding machine" at home, and the small branch my mother managed when I was a kid had adding machines at each teller window. In both cases, I'd sit and play with the adding machines every chance I'd get. (Also, the teller drawer and its money was fascinating -- most especially that one $20 bill under a little spring thingie that I mustn't touch because it would set off the alarm.)

When I write "adding machines", I'm referring to this contraption, which uses what TFA refers to as the "comptometer's layout".

As ChurchHatesTucker writes, each column of keys is a digit, and for a "0" you'd not press any key. Also, these were adding machines, so this is from which the ten-key input fomat originated, where (as I think of it), subtraction is the addition of a negative number.

It's interesting that even thirty years ago, when I was a Radio Shack clerk, I had a customer return a ten-key because he claimed it was broken. When I showed him how it should be used, he refused to believe that was a business standard. I imagine that the majority of under-30 folk would be completely flummoxed.

Finally, the touch-tone (DTMF) (!) system uses a pair of tones together from, respectively, a group of three (1209Hz, 1336Hz, 1477Hz) and a group of four (697Hz, 770Hz, 852Hz, 941Hz). These correspond to the columns and rows and use a very simple mechanical contact switch and wiring to produce a unique pair for each key. On these old Bell touch-tone phones, if you press two keys in the same row or column, you'll hear only the corresponding row or column tone, respectively.

The original rotary dial phones had a similarly simple, elegant mechanism -- at each digit, the rotating dial briefly closed the line's circuit, opening it again as it passed, with countering springs to make the motion/timing uniform. The switch recognized a digit by the regularly timed number of clicks. Thus, even today you can dial any phone number qith merely the two exposed wires of the phone line: touch them together for at least half-a-second to get the switch to send a dial-tone, then just separate and touch them together a number of times for each digit (keeping them touching a slightly longer moment between digits). If you have a speaker, that's a you need to get a dial-tone, make a call, and hear someone answering "Hello? HELLO?". (Ask me how I know all this and, later due to further discovery, why Bell Security came knocking on my door when I was a teen.)

There's also the Bell Labs story of the (supposed) naming of the "#", which probably is familiar to most people here. (tl;dr: "octothorpe"was a joke that nevertheless made it into some documentation.)
posted by Ivan Fyodorovich at 3:16 PM on September 20, 2018 [10 favorites]

Some banks have a telephone-like keypad on their ATMs but provide a calculator-like keypad when the teller asks you to set your PIN.


In the UK, all ATMs and chip-and-pin terminals are telephone layout - at least, that I've encountered. In China, at least one bank's ATM is calculator layout.

And this is how I found out that the number of incorrect PIN attempts it takes from China to trigger a UK bank's anti-fraud account lock is one. Also, how much fun it is being in Beijing with no money and no working plastic. Also also, how much extra fun it is to try and remove the teeth of a UK anti-fraud algo-dog from one's account, from Beijing.

I am not a fan of this UI crapulousness.
posted by Devonian at 6:30 PM on September 20, 2018 [3 favorites]

Ivan Fyodorovich: "Thus, even today you can dial any phone number qith merely the two exposed wires of the phone line: touch them together for at least half-a-second to get the switch to send a dial-tone, then just separate and touch them together a number of times for each digit (keeping them touching a slightly longer moment between digits). "

Moreover, you can dial the phone just by tapping the "hook" switch where the phone goes; no need to use bare wires. That's why on all the old timey movies they were tapping the phone a bunch of times, saying "operator? operator?". They were "dialing" a zero.
posted by readyfreddy at 2:33 AM on September 21, 2018 [2 favorites]

Finally, the touch-tone (DTMF) (!) system uses a pair of tones together from, respectively, a group of three (1209Hz, 1336Hz, 1477Hz) and a group of four (697Hz, 770Hz, 852Hz, 941Hz).

Actually, it's two groups of four tones, but the column for 1633 Hz, which is associated with set of buttons labeled A, B, C, and D down the right side of the keypad, has long been phased out of common use in consumer and commercial grade phone systems in the US. These buttons were originally intended to be menu buttons for interacting with automated systems by phone.

Phone companies sometimes do still use those tones internally for network control, so their technicians' gear will come equipped with the full 16 button keypad. Up until the early 90s, the US military also had a phone system that used the extra 4 right side buttons for specifying call priority.
posted by radwolf76 at 6:17 AM on September 21, 2018 [2 favorites]

That's why on all the old timey movies they were tapping the phone a bunch of times, saying "operator? operator?". They were "dialing" a zero.

To dial 0 (operator) requires ten relatively precise taps. (Source, I'd practice dial that way for grins, it's tougher than you'd think. )

Back in party line days, throwing a fit like that might attract the operator's attention, but probably not her affection.
posted by ChurchHatesTucker at 12:10 PM on September 21, 2018 [1 favorite]

the column for 1633 Hz, which is associated with set of buttons labeled A, B, C, and D down the right side of the keypad, has long been phased out of common use in consumer and commercial grade phone systems in the US.

All touchtone phones can still generate them, though, as the chip that generates the tones has a 4x4 matrix input with that one line unconnected. At least, that was the case when I last looked at this seriously in the 1990s. You can easily wire up four switches and get your A-D tones back - and who knows what might happen if you play them to your carrier?
posted by Devonian at 12:00 PM on September 22, 2018 [3 favorites]