A data acquisition interface system for translating real-time randomly occurring complex input signals into data processing usable form for transmission to an online data processing system. The system includes a plurality of interchangeable data acquisition components of the monitor register, scaler/timer and analogue to digital converter type which are activated by external means for gathering data, counting inputs, measuring time and making analogue to digital conversions and an interface control unit for organizing the data transfer from the components to the data processing system. The occurrence of an input signal, the time coincidence of two or more input signals or the presence and absence of input signals or the like are termed events. In response to the occurrence of an event, the interface control unit initiates a sequential component data transfer from the components associated with the event preceded by a word identifying the event. Events are processed in numerical sequence, but processing may be selectively modified to permit processing in priority sequence. Events may be programmed to exclude other events which share a common component.