Have you ever seen the movie "Pushing Tin?". It's not really all that good, but it does feature air traffic controllers a lot. One thing you may notice while watching this movie, which was made in 1999, is that the screens they look at featured both he blips and the transponder codes. While I realize this is a work of fiction, it's amazing that they would have this technology showcased ahead of 9/11. Do you think it's possible that they actually do receive the information from radar (to locate) and transponder (to identify) on th same screen? The fact that I asked a friend isn't that good so far as asking for evidence, so I figure this Angelina Jolie classic might serve as an aid.
I'm pretty sure that both radar and transponders have been displayed on the same screen since the 1980s. I'll see if I can find proof online, but for now Pushing Tin will have to do.
