more complicated aircraft will feature master warning and master caution lights/switches. in the event of any red or yellow annunciator being activated, the yellow or red master light, usually located elsewhere in the pilot's line of sight, will illuminate. in most installations they will flash and an audible alert will accompany them. these "masters" will not stop flashing until they have been acknowledged, usually by pressing the light itself, and in some cases the audible alert will also continue until this acknowledgement. on some aircraft (most boeing airliners, for example) the "masters" will also flash briefly and the audible alert will sound whenever the autopilot is disconnected, as an additional reminder to the pilots that manual control is now required.