circuitbreakers essentially cut off electricity to various system on the aircraft. in the case of fire or smoke. and ultimately in the case of the 777 and newer generation aircraft like the 787, the they are a bit more spread out on the aircraft. on the 777 in particular there are circuit breakers over the heads of the crew which control things like the radios and transrespond tran transponders but on the 787 it is different. with you but on the single-aisle aircraft that fly the medium and short-haul routes that are used to flying between, for example, washington, d.c. and chicago, the acars system, radios, voice recorder are all directly accessible on the flight deck behind the pilot s heads.