Instant Replay In College Football?

Can anyone explain the instant replays in college football to me? Is it like a pro system, where the team needs a time out for a challenge or do they always do it if the coach requests it or what? I totally can't understand what is going on with this.

yah

i don't understand either. there was also something like that in the nfl where the coach couldn't challenge for some reason and then another time in the nfl where the equipment wouldn't work for 2 minutes so they automatically lost the challenge. the whole video replay system is stupid.