The four systems described here illustrate the qualities required to make a system deserving of the appellation ‘information system’. We have shown that while the hallmarks of traditional systems, data, processing, output and feedback may not be obvious in some non-traditional systems, using a wider terminology allows systems with apparently quite different qualities to be included under a broader definition of IS. Adopting the terms signal and transformation, taken from the general systems and semiotics literature, and adding the concept of action, we have proposed a common terminology that legitimises the label information system not just for traditional systems but also for the routine manual systems described. This approach makes a novel contribution to the IS literature and will assist IS researchers in classifying a wide variety of systems as within or outside the information systems category.