Hey guys, I'm only a few weeks away from doing some of the exams for the ATPL(H) and have been doing some revision. I came across this question a while back and it raised my eyebrows slightly. Back then I just committed the answer to memory, but now I'm curious.
Q: The radar controller suspects that you are experiencing unlawful interference. What should he do to confirm this with an auto decoder unit? (with no mode A interpretation?)
A: Switch from 7500 to 7700.
So how on earth can a controller decide that we have been hijacked by switching codes on his unit without us indicating it first on our unit? And if we squawk 7500 shouldn't little flashing thingys appear on his screen along with little alarm bells without him having to switch codes on a decoder unit? Any insight would be greatly appreciated. Even if that insight is that I'm a total retard for not getting this totally simple concept!!
On another note, this is the first time I've had something to post in the ATC section of PPRUNE. I'd like to take this opportunity to thank you guys for your support on the ground.