Why 9 and not 10 minutes snooze?

Factual Questions
1

My apologies if this has been asked before.

Every alarm clock I’ve ever owned has been pre-set with a 9-minute snooze feature. I’ve been vaguely wondering why for decades.

My theory: The original designer of the snooze feature added it to an existing design. The design he worked from could only alarm on-the-minute. It made sense that the snooze-alarm go off 9 full minutes (plus however many seconds) after the button was pressed, which meant that the second ringing occurred 10 minutes after the first. Later designers who copied this design didn’t realize the reason for the 9 minutes and blindly employed it as a standard, ignoring the seconds that had elapsed since the original alarm signal (and, sometimes, the remainder of that same minute).

Please post if you can relieve my ignorance or have a better theory.
p.s. Presently I use my phone as an alarm clock. It has a timer feature which I pre-program and use in lieu of the ubiquitous 9-minute snooze. I find that 15 minutes works great for me as I always only use it once. My previous phone had a 5-minute snooze which, paradoxically, tended to make me late too often, as I developed the habit of hitting it multiple times.

2

Actually, there’s no shortage of theories in Cecil’s column here:

I’d heard, elsewhere, and often, that it was a certain economy of the electronics – counting to 10 requiring two relays/registers/tubes/whatever, counting to nine requires that just one do it nine times. And it has just sort of stuck.

3

Thanks Arkcon, I should have known that our Perfect Master had already covered it!

I like that my guess is pretty close to Cecil’s preferred answer.

I suppose we can close this one, unless anyone has something to add.

It’s actually bedtime for me, so I’ll check back in the afternoon–assuming my phone goes off as programed.

4

Interesting that the Cecil column is from 1999! We can’t escape those darned nines…TRM

5

FWIW, the clock I use in my bedroom has a 10-minute snooze.

6

This is the culprit. The TTL 74 series were the shizz-nitz back in the day and were the basis of all digital circuitry. When the first digital alarm clocks from Radio Shack came out, they used these counters (I built mine from a kit).

7

IIRC, the first snooze alarms were on mechanical clocks of the rotating flip-card variety, and the 9 minute delay is derived from the rotation of the minute wheel.

I could be wrong though, I read this many many years ago.

8

Cecil’s column has a pretty good argument against most of the theories in this thread:

9

Mine, too.

10

My alarm clock has an adjustable one. The default is 9 but I can set it anywhere from 5 to 30 minutes.

11

Mine is seven minutes

12

I always thought it was a variation on the $5.99 price deal.
If you set your alarm for 6:30 (on a digital alarm clock), you can hit snooze once and the clock will say 6:39, which seems almost like 6:30. If the clock said 6:40, it would seem later and you might enjoy the ‘snooze’ less.