Why does the alarm clock snooze button give you nine extra minutes, not ten?

http://www.straightdope.com/columns/read/1361/why-does-the-alarm-clock-snooze-button-give-you-nine-extra-minutes-not-ten

by peteforde • 13 years ago

196 110 13 years ago

straightdope.com

failrate• 13 years ago

I have a problem with this explanation, because on my grandmother's ancient electromechanical clock (with radium painted hands), the snooze alarm interval was user-defined between a few minutes to almost an hour. I'm leaning towards someone cleverly using the numeric rollover to trigger the interval, and then every subsequent digital clock cargo culting the design.

happywolf• 13 years ago

I always wish iOS allows me to set the snooze interval...

therandomguy• 13 years ago

I thought it was to disorient you a bit. If you typically snooze three times you know you have to be out of the bed at 8:00 sharp (with 7:30 original). Easy for your brain to latch on to that. Now with 9 mins…

aeontech• 13 years ago

I can do multiplication in half-conscious state easily if it means a few more minutes of precious, precious sleep...

Besides you really just need to remember how to do subtraction, not even the multiplication table

  var snooze = 3
  snoozety (30) minutes minus snooze (3) minutes = twenty seven

Now, if the alarm clock required you to solve a calculus problem, that'd be a bit more challenging :)

DanBC• 13 years ago

"Or maybe, since the clock is counting (typically) the power cycles from the wall socket, it's because [...]
Engineer's comment: Nice try, bub, but clocks don't count that way.

What? Some clocks do count that way. That's why you can buy converters.

http://www.electric-clocks.co.uk/60hz50hzfrequenc.html

Thiis module takes the 60Hz input and produces a 50Hz output to ensure the clock keeps the proper time. The module is supplied with 9vac via a UL listed power supply adapter. The clock has had it's coil rewound to work at 9vac.
No changes to the movement - no altered wheelwork. If the clock is ever required to run in the UK it is as simple as providing 9vac from a UK 50Hz power supply and bypassing the convertor.

https://en.wikipedia.org/wiki/Electric_clock#Synchronous_ele...

A synchronous electric clock does not contain a timekeeping oscillator like a pendulum, but instead counts the oscillations of the AC utility current from its wall plug to keep time.

Here's a nice page telling you how to build one. It has plans for both 50 Hz and 60 Hz. http://sound.westhost.com/clocks/sync.html

codezero3• 13 years ago

edit: It sounds like the first alarm clock with a snooze might have been synchronous so maybe it's worth thinking more about that :)

http://en.wikipedia.org/wiki/Telechron http://blog.onlineclock.net/evil-snooze-clock-history/

It's a bummer the Wikipedia article for Alarm clocks cites the straight dope article which links to some suggestive information that is totally missing now. It's too bad that Wikipedia doesn't store source information that is important for verifying the statements in articles in case the linked source disappears (or does it?)

originally, and probably wrong:

Yeah, some clocks used this, but I don't think it was most clocks and unless the first clock with a snooze functionality was this type, it doesn't give any more insight into why 9 minutes was chosen.

Groxx4• 13 years ago

It's too bad that Wikipedia doesn't store source information that is important for verifying the statements in articles in case the linked source disappears (or does it?)

Good reason to donate to www.archive.org :) It's probably accessible there, and the citation should include a date you can rewind to. Not that that's ideal, but it's at least verifiable, and probably available now if not forever.

nwh2• 13 years ago

So many devices rely on the timing of the waves that the generating companies actually keep count and then adjust the speed to make up any they might have missed!

wyager• 13 years ago

That's not at all why grid timing is so precise.

Multiple generation systems feed into the same grid. If they're out of phase by even a few milliseconds, that translates to huge power losses. If power generation companies didn't synchronize to high precision, they would lose a lot of power and probably break some equipment.

raverbashing3• 13 years ago

Yes, some alarm clocks do count the cycles "from the wall".

Source: I helped a friend hack his clock to change his alarm clock from 60Hz to 50Hz.

frenchman_in_ny• 13 years ago

I'm fairly curious about how you did that, and if the same is doable for larger load devices (60Hz -> 50Hz or 50Hz -> 60Hz).

nodata• 13 years ago

So instead of measuring vibrations from a crystal, they are measuring cycles from the wall? Why?

exDM69• 13 years ago

In the past, the mains AC frequency was a cheap and accurate way to keep track of time. A lot of devices relied on the mains frequency.

Why does your modern day LCD monitor have a 60 Hz refresh rate? It's legacy from 1950's vacuum tube televisions that synced their beam with the mains voltage frequency.

marcosdumay• 13 years ago

Creating a pure enough crystal and cutting it in the right format was once very expensive.

There was a time when all the clocks relied on mechanical timers, and a MW sized electrical generator is more stable than anything you can put at your living room.

huhtenberg• 13 years ago

What? Some clocks do count that way. That's why you can buy converters.

And it's also why your microwave clock is always off :)

X-Istence7• 13 years ago

Microwave clock, oven clock, your VCR/DVD players clock, and your alarm clock (if it is the plug-in kind that doesn't use a crystal to keep time).

vidarh2• 13 years ago

What? Some clocks do count that way.

Lots of stuff used to... The realtime clock in the C64 (almost nevery used) worked in that way too. (it was one of a handful of things that depended on AC; you could power the machine off a 9V battery if you were ok with certain minor functionality not working)

Theodores• 13 years ago

This all began in the 1970's when National Semiconductor brought out a series of integrated circuits for alarm clocks, clock radios, clocks for cars and so on. These chips included the LED display driver and the timing clock usually came from the mains.

Here is an example with the page of the data sheet regarding how the snooze function works:

http://html.alldatasheet.com/html-pdf/9252/NSC/MM5387AA/168/...

When the alarm goes there is a 'latch' that is operational for 59 minutes. Pressing snooze does not turn this 'latch' off, it suppresses the alarm output for 8-9 minutes. Turning the alarm off is what resets the 'latch'.

Chips of this era worked on BCD - BCD ruled once upon a time, when people did things in FORTRAN...

I don't think that National Semiconductor deliberately sought to emulate the snooze time of analog alarms from a previous era, it just was do-able to do 8-9 minutes in available silicon.

gmrple• 13 years ago

BCD was my thought as well. For the uninformed: http://en.wikipedia.org/wiki/Binary-coded_decimal

TaqPolymerase• 13 years ago

I think the author might be referring to clocks not counting in binary, rather than clocks not counting off power cycles. Full text:

(6) "I figured it was actually 512 seconds (2^9)," one informant speculated. "Or maybe, since the clock is counting (typically) the power cycles from the wall socket, it's because nine minutes is 32,400 cycles, very close to 2^15 (32,768)." Engineer's comment: Nice try, bub, but clocks don't count that way.

dfox• 13 years ago

It is also worth noting that most alarm clock chips not only keep time by counting AC cycles (often with fallback to 9V battery and suitably divided 32768Hz crystal) but also derive timing of all other internal functions from it. For example when LED display is multiplexed into two sections (as it often is) there are no common electrode drivers and instead the display is directly connected to two 1-way rectified taps of mains transformer. Economies of scale in AC-powered radio clocks are such that center taped (or even multi-taped as required for things like LM8562, which seems common in European clocks) transformer is significantly cheaper than two additional transistors.

And LM8562 and this timing of everything off mains is the reason why many modern alarm/radio clocks have that convoluted interface for setting time and alarm with two buttons that decrement setting by one minute and increment it really fast (ie. 50/60 minutes per second).

[Edit: 50/60 minutes per second, not 25/30, datasheet says that this rate is not dependent on rate of pulses on the setting pin, but I think that nobody really tested what will happen if the button is connected to anything other than mains frequency]

jnsaff2• 13 years ago

So at 7PM in the UK all the alarm clocks will be a little slow ?

http://www.bbc.co.uk/britainfromabove/stories/people/teatime...

codezero3• 13 years ago

This still skips the reasoning for even an imprecise 9 or 10 minutes. What information guided that decision? Ignoring the precision is a separate practical issue.

jarrett• 13 years ago

I can imagine it went something like this:

Engineer: "Hey boss, how long did you want the snooze timer to run?"

CEO: "Oh, I don't know. Not too long, not too short."

Engineer: "What does that mean? Like 10 minutes or so?"

CEO: "Sure, I guess that would be fine. Just get it done."

Since this is an alarm clock, not a nuclear power plant, it's entirely conceivable that the decision was made very casually. It could have just been someone's gut feeling that 9 or 10 minutes felt right.

codezero3• 13 years ago

Sounds about right, but it would be awesome to know for sure, but maybe I should be getting something done too :)

pgrote• 13 years ago

A shame you cannot get to the old link in the article.

https://web.archive.org/web/20021001101305/http://users.rcn....

toomuchtodo• 13 years ago

http://web.archive.org/web/20000830091714/http://www.ultrane...

ctdonath• 13 years ago

I want to know why the alarm clock off button is built like something you'd not want to use. Snooze is a big fat easy button; off is a small switch hidden among other switches and usually on the bottom back of the device, requiring turning off to stop the alarm and then turning the switch back on to re-enable it for the next day. Once I'm awake, I want to shut the alarm up - period - without having to find and fiddle with a hidden control. Or am I seriously missing something obvious about standard cheap alarm clocks?

dlubarov• 13 years ago

I think the idea is to make it harder to semi-consciously turn off the alarm clock before you're really awake.

_wmd• 13 years ago

Because for people like me, unconscious zombie-like bears who will dig through concrete walls with bare hands in order to quiesce the source of the disturbance of my crucial slumber, while maintaining no memory of the demolished wall should I be successfully woken 10 seconds later, easily shut off devices simply have no effect.

I've woken up a few times on the floor curled around the power cord to the alarm clock, torn from the wall (or to find a phone in 15 pieces and a new dent in the wall).. many, many people like me

MiguelJones• 13 years ago

Maybe it's just a simple matter of whoever implemented the snooze functionality picking 9 minutes as the value. The one minute difference between 9 and 10 minutes is probably negligible.

dwrtz• 13 years ago

It leaves you with an extra minute to decide if you're going to hit snooze again.

Groxx4• 13 years ago

Dunno. All the alarms I've owned have been 6 or 7 minutes.

Another question: why does the alarm clock blare non-stop until you turn it off, rather than beeping a couple times and then going silent, giving you a moment to get up and turn it off without annoying the living hell out of everyone who doesn't have to get up?

Current theory: alarm clock designers never marry.

colanderman2• 13 years ago

My wife's alarm clock works that way. It's pleasant yet effective.

Groxx4• 13 years ago

My wife and I have mostly switched to the Jawbone Up since it's a silent, vibrating alarm, and we each have a different one. Audible is now the backup.

But! What alarm is this? It sounds wonderful. Mine is pretty old and starting to die / possibly flaky, I might have to pick one up.

kijin• 13 years ago

Me too. This is the first time I've ever heard of alarm clocks with 9-minute snooze intervals.

The TIMEX clock I've been using since college has 8-minute intervals, and the alarm clock app I have on my phone has 10-minute intervals by default.

TeMPOraL• 13 years ago

Depending on how tired (or drunk) I went to bed the previous night and how much time I gave myself for sleep, it might take even a few minutes for me to finally wake up to the alarm signal. Anything short would be totally ineffective for me.

Also, this ensures the alarm clock does its job - either you wake up yourself, or your angry family members wake you. Both ways, you get up when you wanted.

Groxx4• 13 years ago

Agreed. So progressively get more annoying, instead of doing the worst possible thing first.

alexkus• 13 years ago

Current theory: alarm clock designers never marry.

But when they do they may end up with their own alarm clock that is impervious to logic, programming or reason.

For a notional 7am setting our little alarm clock wakes up one of us (a seemingly random choice) usually sometime between 6.15am and 7.15am. Very occasionally it malfunctions and wakes us both up at 3am.

bencoder• 13 years ago

I used to have a great alarm clock that would beep progressively faster until it was pretty much just a constant tone. It would start off with a beep every four seconds or so, for about 4 cycles, then go down to about 2 seconds per cycle, then 1, then half etc. I want that alarm back.

The snooze was on 8 minutes but I could press the snooze button multiple times to increase the time. So if I wanted a 24 minute snooze I could wake up and press it 3 times and it would go off in 24 minutes.

mgkimsal• 13 years ago

I built a heathkit one in the 80s. It had a 7 minute snooze. My current one, bought in .... 2000? is a (IIRC) 7 minute snooze. Not sure where 9 minute ones are.

Steuard• 13 years ago

I always guessed that they wanted something around 10 minutes, but they wanted more than one visible digit to change each time to make it more obvious that time had passed. (That is, a sleepy person might be more likely to mistake "7:20" for "7:00" than they would be if they saw "7:18".)

But that wouldn't be relevant with old analog alarm clocks, which evidently had a 9-10 minute snooze, too.

atoponce• 13 years ago

I can't say if this is why it's 9 minutes, instead of 10, but when the alarm goes off, and I hit the snooze, my brain is anything but fully conscious. So, I see the time "06:00" then "06:09" rather than "06:10", and I know the time has changed- because of the 9. At the next interval, it's "06:18" rather than "06:20". Again, an obvious time differential for my brain. Instead of just 1 number changing every ten minutes, 2 numbers are changing.

06:00 06:09 06:18 06:27 06:36 06:45 06:54 07:03 ... etc.

Versus:

06:00 06:10 06:20 06:30 06:40 06:50 07:00

Not enough numbers are changing for my brain to latch on in its semi-conscious awake state, if the time is only changing by 10 minutes. Changing by 9, and it's clear the time has changed, and it's a new time. Thus, I'm not thinking only 10 minutes have passed, when the truth is that 40 minutes has actually passed.

tempestn2• 13 years ago

Huh, never thought of that. That probably is kinda handy.

contingencies• 13 years ago

This seems closer to engineer-thought reality, IMHO.

Also, some people like to snooze multiple times... a low number of times, to be precise. They do this as a regular thing.

If I were such a person and I were to snooze thrice, I would know I am really in need of getting up if 30 minutes has elapsed. There is an up to one minute procedural loss on sorta-wake-up, activate-limb, smash snooze button, go back to bed. So I know I'm definitely not sleeping over my 30 minutes of triple-snooze allowance if I have a 9 minute timer. (Yes, the timer could be set from the trigger time rather than the re-snooze time, but at least some ancient embedded devices probably did not function in this way)

To further compound this line of thinking, we should remember that getting out of bed is not the only use for timers. Another would be kitchen timers where people might really, really, really want to get the pie out before it burns and some default allowance for human fuzzy foibles is therefore a useful feature.

Perhaps we should replace the title of this post with: Engineers: "Nine; it made sense at the time".

cstrat• 13 years ago

This makes the most sense to me!

Juha• 13 years ago

How about this for a reason: One of the first big snooze clock manufacturers choose 9 minutes for some random reason and the rest followed thinking: "There must be a reason they choose 9 minutes, it sounds specific. Lets have our snooze be 9 minutes too."

I was expecting find some some highly researched psychological quirk to be the reason in the post. I guess reality is just more random and coincidental. Reminds me of the way QWERTY came to be the standard (https://en.wikipedia.org/wiki/QWERTY#History_and_purposes).

ordinary• 13 years ago

That does not explain anything though, it just moves the problem. As the article also points out, what was the original "random reason"?

tempestn2• 13 years ago

I had always just assumed it must have been an ease of implementation thing. (Explanation 8.) Their suggestion that you could just check the 10s column instead of the 1s is misleading. You would have to test both the 10s and the 1s column to get a 10 minute differential, unless the original alarm time happened to be a multiple of 10.

MRSallee• 13 years ago

8:00:00 am

alarm clock begins beeping

8:00:15

I actually begin waking up

8:00:45

I manage to get up and silence the dumb machine

8:10:00

alarm wakes me up again after initial snooze, ten minutes after I intended to be awake

If the snooze went in ten minute increments, and a person was fond of snoozing, after a handful of snoozes the time delay between alarm sounding and snoozing would add up and throw off the mental calculation.

"I've hit the snooze five times, it must be 8:50, oh shit it's actually 8:55, FML," versus, "I've hit the snooze five times, it must be 8:50, oh hey it's actually only 8:47."

itchitawa• 13 years ago

This is also my pet theory too. You can mentally count and err on the safe side.

IbJacked• 13 years ago

That's been my theory, as well.

kseistrup• 13 years ago

hrkristian• 13 years ago

That's a good theory.

I have multiple alarms on my phone, as sometimes I'll turn off an alarm completely in my sleep. I put these alarms teen minutes apart, call it OCD. Snooze time of nine minutes makessense a lot of sense fire my part.

andyhmltn• 13 years ago

I do this. I set one alarm for an hour before I'm meant to be up (I usually don't remember this), one half an hour before, one on the actual time and then in smaller and smaller increments until I'm so annoyed with turning it off that I just get up.

colszowka2• 13 years ago

For me this looks like this: "I've hit the snooze five times, it must be 8:50, oh hey it's actually only 8:47. I SHALL SNOOZE ONE MORE TIME!"

mkopinsky• 13 years ago

You can count to five while still snoozing? I know I couldn't...

weavie• 13 years ago

The app on my phone makes me add two two digit numbers together before it switches off. It gives me just enough time to engage my brain to calculate how many more snoozes I can get away with.

panacea• 13 years ago

For me, iOS 7 requires just that little bit more mental effort to grok the interface that my brain engages enough to calculate.

Thanks Ive!

famblycat• 13 years ago

Multiplication tables are too deeply ingrained in my brain for that to work on me.

nrivadeneira• 13 years ago

My alarm does 10 minutes regardless of how long I take to wake up. In other words, if I set the alarm at 8:00am, wake up and hit snooze at 8:03am, the alarm will still go off again at 8:10am, not 8:12am. For a digital alarm clock, it seems pretty trivial to just add 10 minutes to the current alarm time.

platypii• 13 years ago

I have always assumed it was to reduce the likelihood of conflicts with future alarms. For example if I set alarms at 8:00 and 9:00, if I've been snoozing the 8:00 alarm, and snooze is 10 minutes, the two alarms will both fire at 9:00. With 8 or 9 minute intervals that is much less likely, and so its easier to see that maybe they are two different reminders. This probably applies more to phones than old school alarm clocks however.

koobz• 13 years ago

Nine is great. I snooze 4 times and it's 4 minutes more time I have than if it were 10 minute intervals. That's 4 extra minutes to ride my bike to work on time for the daily standup at my startup.

Now I suppose I could just set my clock 36 minutes later and get 36 minutes of quality sleep. But I think I actually enjoy those short snooze button dreams. And I savour every minute. Again and again and again and again.

tsotha• 13 years ago

I always assumed this was a function of hardware on the original snooze-enabled digital clocks. If you reset a decade counter chip (like the CD4017), you get a rising edge on the carry out pin after nine clocks.

BarkingOven2• 13 years ago

I'll tell you exactly why it's nine minutes. Because in the olden days where everything was made with discrete components, the math of 9 minutes is WAY cheaper.

Let's say it's 6:00, and you hit the snooze button. Save the current value of the minute minus 1, into a comparitor, Trigger the alarm when the comparitor goes off automatically.

If you save the current value into the comparitor, the alarm triggers immediately. Now you need to add delay logic. Just use current minus 1, since it's only a few half-adders.

You can't use the high order minute digit because then your snooze length will depend on your current low order minute digit. Any logic to compensate starts adding a multiple of the number of components required.

sajidnizami• 13 years ago

Your argument makes most sense around here :)

gojomo• 13 years ago

Thank you, I would bet on this. Examining an early digital clock with 9-minute snooze could probably confirm that the 9 minutes is implemented using some smaller number of components than any 10-minute system could be.

I also vaguely recall that such on such clocks, the alarm itself (if not silenced) would tend to run for 9 minutes before self-silencing. The same logic might apply: it's the longest finite interval that doesn't require some sort of multi-digit carry-logic.

I wouldn't be surprised if early circuit layouts even made it so that the wiring to toggle some [digit ± 1] triggering state was shortest/cheapest, in a circular arrangement, compared to any other potential offset. (I don't even think there was anything binary in the earliest digital-display clocks, rather some [10m, 6h, 24h] or even [10m, 6h, 12h, 2meridiem] cyclical counters.)

mtdewcmu• 13 years ago

This rings true.

mehwoot• 13 years ago

It was established in the age of mechanical clocks. Because of the way the gears were generally configured, the two sane options were 9 minutes or a bit more than 10. They chose 9. Digital clocks followed suit.

raverbashing3• 13 years ago

"In the old days when everything was made with discrete components" and you talk about "comparitor" (comparator) and "minus one"

No, this is too advanced.

For that you would be looking at 4 bits storage + comparator + the "minus one" circuit (which is very complicated) for a BCD counter.

mhandley• 13 years ago

You don't need the "minus one" circuit. Just always store the previous minute value whenever the minute is incremented, and then latch that value when the alarm goes off.

troels• 13 years ago

But are clocks using a base-10 counting system? I'm thinking no.

colomon• 13 years ago

The oldest digital clock my family had used a mechanical display, so it had ten values for the right-most digit, six for the next, and twelve for the left-most. So this explanation would definitely make sense for it.

But I don't recall if it actually had a snooze button...

Brashman• 13 years ago

Usually BCD (http://en.wikipedia.org/wiki/Binary-coded_decimal)

vidarh2• 13 years ago

In the olden days, our clocks were analogue/mechanical. Even the ones showing digits.

striderhiryu• 13 years ago

Maybe just because it takes around one minute from the time the alarm starts to ring and the time the sleepy-head presses the button and eventually gets up. Better have a minute earlier than later.

erichurkman• 13 years ago

I prefer to subscribe to the idea that it was an off-by-one error myself.

badman_ting• 13 years ago

Moral of the story: Worse is better :)

blahedo• 13 years ago

I've been using my cell phone as primary alarm clock for years, and it always bugged me, for reasons I can't even articulate, that the snooze interval was "wrong"---ten minutes on one phone, five on another. When I finally got my Android phone and could find my own alarm app that let me configure the snooze time, I was inordinately pleased. 9 minutes it is. :) (Alarm Clock Plus, by the way---has a few other nice UI features as well.)

benatkin• 13 years ago

Is there a good documentary about alarm clocks?

splinter_head• 13 years ago

On an old alarm clock of mine, the snooze started at 9 minutes, then went down to 8, then 7 and so on. this allowed exactly 45 minutes of snooze. Something from that may have been brought into modern alarm clocks?

zvrba• 13 years ago

Am I the only person who manages to wake up almost instantly and never uses the snooze function?

jbrooksuk• 13 years ago

I was wondering this, just this morning as I hit snooze. Thanks HN, you've done it again!

napolux• 13 years ago

My alarm clock gives me 8 minutes. Now what?

mrweasel• 13 years ago

Every single alarm clock I've had has given me seven, and I always wondered why.

rgf• 13 years ago

I always thought it was 9 minutes to have 10 minutes of total delay with 1 minute ring time. So that if you don't do anything it keeps ringing every ten minutes.

If you hit snooze it just stops ringing earlier.

I think it's optimised to ring periodically in the worst case scenario (when you don't wake up). With earlier snooze it's just easier to keep the 9 minutes worst case implementation, instead of taking into account the time you hit snooze and adjust the snooze time to reach the 10 minutes total delay between rings.

jalanb• 13 years ago

I came to the comment page to say that it's pages like that that make me grateful for the internet.

Then I read the comments - actually, it's pages like this that make me grateful for the internet.

smoyer• 13 years ago

A nice parallel to the question "Why do I click on a floppy disk to save my file?"

jmpe• 13 years ago

Oh, there are a few more like that:

- there's a very good chance that the touch-pad in your new laptop uses the PS/2 protocol to communicate with the system

- why do I need to address cylinders/heads/sectors in a flash block device? I can understand sectors (block addressing) but cylinders and heads? It's FAT/EXT4 legacy, but the translation layer is still there in many OS-es.

- I recently wrote a driver for an LCD. I could have sworn I was accessing a CRT: front porch, h-sync pulse, back porch, v-sync, ...

brechin• 13 years ago

My clock DOES have a ten-minute snooze. I know previous clocks I've used had a 9-minute snooze, but currently when my alarm goes off at 6:00, I hit snooze a few seconds later, then a few seconds after the clock displays 6:10, it alarms again.

redblacktree• 13 years ago

Mine is adjustable. I have it set to 3 minutes. I still often snooze 5-6 times, but now it costs me ~20 minutes instead of an hour.

aiaf• 13 years ago

I set the snooze on my phone alarm to 20 minutes, which is the standard for the Uberman polyphasic sleep practice. Feels good enough.

Why does the alarm clock snooze button give you nine extra minutes, not ten?

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