There are two different electronic timing systems set up with gates at 10yd, 20yd, and 40yd line.
They are both started manually.
They are there only to provide the hand timers with something to compare their watches to.
The unofficial times you see reported on the television are hand times. The official times are usually an aggregate of the hand time and the laser; although this is inconsistent because it’s not always an accurate average of the two.
The laser times are not revealed to the public; however, I’ve seen them and they’re generally .10 slower than the unnoffical times.
Also important to note is that all the NFL personnel you see in the bleachers, on the 10, 20, and 40yd lines, have their own stop watch and data recording sheet.
As a result, while the NFL network publishes their version of the times on the TV and internet, each of the 32 teams has their own version of the time according to what their scout/coach recorded on their respective watch.
My suggestion to viewers is to accept the unofficial times as a reference point because those are hand times. If you want to form some sort of comparison to track sprinters then add the accepted differentials for human error and no reaction time and make the necessary conversions from the first 40yd segment of a 60 or 100m and you’ll get an idea of how these American footballers compare.