Any engineers on board? Zero on the shot clock, no horn
 

This has been bothering me for a week.

Had a dead ball situation with zero on the shot clock with no horn in a game last week. No biggie. We played on.
(NCAA 2-11-9) When the shot clock indicates zeros but the shot-clock horn has not sounded, the shot-clock time has not expired.

Until then, I didn't believe it was possible, as I always observed shot clocks delaying a bit before the display changing from 35 to 34 (or 30 to 29 for women) implying the display won't change until the internal timer gets to 34.0 or 29.0. I've since tested shot clocks myself to confirm there is, in fact, a "delay", in case we have an end of game situation where clock differential comes into play.

My question:

Any engineers here who can explain the mechanics of the shot clock? Not just theoretical, but someone with experience with the architecture of shot clocks.

My brain has me believing there's actually an extra 0.9 seconds coming into play on the clock.

Consider:

* Not an operator error or reaction time question.
* I realize the rule book doesn't cover (and thus, not allow) discussing tenths of seconds for shot clock. This is what's racking my brain.

Someone please help so I can get some sleep!

Yes, possible. The horn signals 00:00.00.

Not an engineer
 

When we had the change a couple of years ago to reset the shot clock to 15 on a kicked ball - the original terminology said "15 & under reset to 15", the next year that changed to "under 15, reset to 15" was told in the NCAA meeting that was because the shot clock doesn't show tenths of a second and you may be penalizing a team who has 15.8 on the shot clock and you reset to "15.0".

Its actually any amount of time from 0.0 up to 0.9. Theres no extra!

Further clarification
 

1) I start the shot clock. NCAA womens 30 sec shot clock.
2) Shot clock runs, but display still indicates 30.
3) I deduce this to mean "30" on the shot clock means 29.1 to 30.0 in actual time
OR:
"30" = 29.1 to 30.0
"29" = 28.1 to 29.0
"28" = 27.1 to 28.0
..and so on until:
"2" = 1.1 to 2.0
"1" = 0.1 to 1.0

So: how is "0" on the shot clock possible without a horn?

My brain tels me if we had zero on the shot clock, this must mean:

"0" = 0.1 to 0.9
"1" = 1.0 to 1.9
...and so on until:
"28" = 28.0 to 28.9
"29" = 29.0 to 29.9
which means:
"30" = 30.0 to 30.9 ?!!!

Does this make sense? Again, there was a delay from starting the shot clock to when the 30 changes to 29.

did both teams get to use the same shot clock?

if yes then dont think about it anymore - its not a big deal.

Here's why it could be a big deal, and why it's bugging me:

NCAA Womens game

30.8 left in 2nd half. Team B just scored to tie the game.

Team A inbounds the ball and advance to midcourt and calls timeout.

Clock stops at 24.9. Shot clock shows 25 (24.1 in actual time?). Table confirms there were no timing errors.

By NCAA rule, you must turn the clock off.
(2-11-10) Turn off the shot clock when a reset situation occurs and the game clock shows less time than that of a shot-clock period.

Team B coach will have a problem. He/she was thinking if we have a shot clock violation, we will still have 0.8 to get a pass and shot off. I would agree.

pizanno - I've had those same little voices in my head over the shot clock. (So, first thing in the morning, get that doctor's appointment, ok? ;))

I believe you're right, in that game clocks (that don't show tenths) drop immediately from 8:00 to 7:59 as soon as it's turned on, which means 7:59 means 7:59.9 down to 7:59.0, and thus, when the clock shows 0:00, the horn won't go off immediately because the actual time is between 0:00.9 and 0:00.1. I've also seen shot clocks that do as you say, where there is a delay from starting it until it goes down a click. However, from what I've seen, the horn goes off as soon as that clock shows 0.

So, my only suggestions to your problem would be:

1) Was the shot-clock horn on? On many scoreboard consoles, the horn can be turned on and off, so in your situation, was the horn possibly turned off at that moment?
2) Is there a chance different manufacturers would make their units operate differently, so that there would be some shot clocks out there that operate the same as game clocks? So, when the shot clock is turned on, it immediately clicks down to 34, therefore, when it shows 0, there is still .9 to .1 actually left.
3) When you "tested" the clocks that showed a delay between starting and showing a change in digits, were you sure those clocks also had a delay between showing 0 and the horn?
4) Have you considered medication? :)

I had the same debate *years* ago. I simply phoned the manufacturer and spoke to a Product Development Engineer.

I suggest you do the same. There's nothing like 411 from the horses's mouth, because even if your logic is correct, which it looks like it is, you're still not an electron inside the circuit, so you don't really know for sure.

While I can't tell you how the specific clock you're referencing works, there are at least 3 common alternatives.

1. Truncate/Round Down...may display up to 0.99 seconds less than what really remains.
2. Round Up...may show up to 0.99 seconds more than what really remains
3. Round Closest...may show up to ~0.5 seconds more OR less than what really remains.

The last is fairly common in the mathematical and engineering world and would translate to:

• 30 => 29.5 - 30.0
• 29 => 28.5 - 29.4999...
• ...
• 1 => 0.5 - 1.4999...
• 0 => 0.0 - 0.4999...

This last option may explain the delay in the display moving upon starting AND the display of 0 without a horn.

One other possibility here is that the game clock circuitry and operation is slightly different from the shot clock circuitry and operation. It is possible that the mechanism to reset and restart the game clock has a slight delay (not intentionally designed this way, but the way it works), while the game clock responds more quickly to the switch?

Real Live Honest To Goodness Engineer!!
 

I'm a mechanical engineer, not electrical..........

From my understanding, during installation of the shot clock a calibration is performed of the horn vs. shot clock reading. The calibration is required due to the time lag inherant in the system: the electronic signal from the timer takes longer to get to the clock and to be displayed than it takes to go to the horn. This is due to 1. the length/type of cable used, 2. the digital to analog multi channel conversion required for the display, 3. the very quick response of horn due to the single output signal required from the timer.

Therefore, a time delta must be added to the horn function of the timer to allow the horn to sound at the same time as the display reads zero on normal play. Unfortunately, the actual timer may be stopped at a near zero situation, under the 0.1 sec mark so that the clock reads zero but if it is still inside the horn offset, the output to the horn will not be sent.

I hope this makes sense......

Hey -- that should be a question on the bi-weekly eofficials NCAAW quiz. ;)

And, I agree that all systems that I've bothered to "test" have acted as you indicated.

As an electrical engineer....
Nope. In most installations, the horn is integrated into scoreboard. The signal travels over the very same wire....same delay.
An electrical signal can circle the globe at the equator in about 0.2 seconds. The distances in a gym, even the largest in the word, can be covered in about 1 millisecond. Way too short for any calibration difference.
There will be no digital-to-analog conversion. The clock and every other element on the scoreboard are digital and the horn is either on or off...also a digital signal.

What does happen is that signal is split, digitally, into its various components. There may be some small delay in the system here but, again, it will be imperceptable and it will actually be uniform to the clock and the horn.

The one major difference between the horn and the board is the speed of light versus the speed of sound. The light from the scoreboard makes it to the eyes of the observer in about 1 millisecond. But, the sound of the horn takes substantially longer. Sound takes about 1 second to go 1000 feet. So, the sound of the horn can take 0.1 to 0.3 seconds to reach the observer....but it will differ dramatically depending on where the observer is located. So, you can't really fire it early...particularly since you don't know that it should even be fired at all.

The only way the clock reads 0 without the horn sounding (short of a malfunction) is that the actual time on the clock is non zero but is below the displayable resolution of the clock.