Swim timing system

Question
How does the timing and scoring system work? How do they know exactly who touched the wall first? Is it visual or is there some type of sensor on the wall? I can't seem to figure it out and it is annoying me. Pleas help, I figure since you swam competitively you would know. Also do the Olympics use the same system as everybody else?

Answer
Hello!
Ok so  to answer your question there are pads with sensors at each end of the pool that knows which lanes hits at what time according to the moment that a swimmers longest finger hits that board. The score board keeps track of those times so that they can be recorded later. The Olympics use the same system as we use to. They have back up timers (people) with stop watches waiting to time the swimmers also just in case the system fails. Each time is recorded exactly, down to the millisecond. Hope this helps! Let me know if you have anymore questions.