cockpit. you just turn the button, it's off. the acars system is a little bit more complicated to turn that off. i don't know if you can do it from strictly sitting in the cockpit or if you have to leave the cockpit and go to the underbelly. how do you turn off the acars system? >> the only reason you'd be pulling a circuit breaker in the cockpit. you could turn off part of acars system. >> that would turn it off. >> the only reason you'd be pulling a circuit breaker in the cockpit by manual operations is to prevent, say, a fire from continuing. it's really to prevent a bus, an electric bus from continuing on a fire path. >> mark weiss, thanks very much. always good to get your explanation. we'll keep watching for breaking news on the search for flight 370. stand by for that. also coming up, cnn's karl penhaul, he's with ukrainian forces right now as russian president vladimir putin, he phones president obama to discuss the crisis. also exhausted searchers tell us