CNN Wolf March 14, 2014 17:18:00
Traffic control or others on the ground where the plane was? >> the transponder's very easy because of the fact that when you're on the ground you are supposed to turn it off. you're no longer needing radar. so that's why the on/off switch is so accessible. the other equipment you talk about, whether it be the radios, and there are many frequencies that they could be using, whether they use the acars system, that's the system that basically transmits what the airplane is do, even the engines are reporting in without necessarily the pilots input. to disable those, that's something far more comp...
Source: archive.org