A process to detect a failure of a constituent system (110 . . . 113) in a system of systems (1) consisting of a number of constituent systems (111 . . . 113) which exchange messages through a communications system (120), in which every constituent system (111 . . . 113) has a global time with a known granularity g, and at least one constituent system creates, at periodic creation times (210, 211) determined a priori from the progression of the global time, a time-triggered life-sign message, the time of transmission (211, 221) of this life-sign message in the time-triggered communications system (120), determined a priori from the progression of the global time, is synchronized with the creation time of this life-sign message, and the time of receipt (212, 222) of this life-sign message, determined a priori from the progression of the global time, is synchronized with the timeout time point (213, 223), determined a priori from the progression of the global time, of a monitor (130) of this life-sign message monitoring the arrival of the life-sign message, wherein an error message is triggered at the timeout time point if no life-sign message has arrived at the expected time of receipt (222).