1. A process for signaling malfunctions of a respirator with single source of energy constituted by the source of respiratory gas under pressure of the respirator, which makes it possible to apply a pulsatory insufflation pressure to a patient to whom it is connected, in which said pulsatory insufflation pressure is compared with an adjustable threshold value (P.sub.s) and an alarm is triggered off if the difference between the maximum value of this pressure and said threshold exceeds a predetermined quantity either by excess or by want, said process comprising the following steps of: creating a pneumatic signal formed by pulses which coincide with the periods when the insufflation pressure is greater than said threshold (P.sub.s), and detecting the appearance of an excessive difference between the maximum value of this pressure and the threshold by observing the difference between a representative parameter of said pulses and a predetermined normal value (t.sub.n, a.sub.n) of this parameter, this value being adjustable.