[instantkevin]

you just have to learn what cops use in your particular area. After about a week or two of driving around with it, you'll know what is what. Go out on weekend nights and on the highway during the day (or whenever cops are out setting speed traps where you live) and when you pass a cop, if he has his radar on, the alarm will sound and bingo! That is the band he is using. After this happens a few times, you'll see the pattern, and then you can be pretty sure what band they use. When you're driving around town it will go off everytime in particular spots, these are false alarms caused by radio frequencies that around that area, just hit the "shut up" button. Around here cops use Ka band, most of the stationary radar (the ones on the side of the road) use X band, and the State patrol uses X band also. A good detector will detect laser, but I have never been clocked by a cop using laser.
Yes, all three bands can potentially be cops. A lot of people don't realize that a radar detector is not a cop detector, it will only sound an alarm if the cop has his radar on. (Learn about "instant-on" radar).
That sucks that they use time gates where you live.