The attenuation and amplification of variety were major themes in Stafford Beer's work in management (the profession of control, as he called it). The number of staff needed to answer telephones, control crowds or tend to patients are clear examples. The application of natural and analogue signals to variety analysis require an estimate of Ashby's "powers of discrimination" (see above quote). Given the butterfly effect of dynamical systems care must be taken before quantitative measures can be produced. Small quantities, which might be overlooked, can have big effects. In his Designing Freedom Stafford Beer discusses the patient in a hospital with a temperature denoting fever. Action must be taken immediately to isolate the patient. Here no amount of variety recording the patients' average temperature would detect this small signal which might have a big effect. Monitoring is required on individuals thus amplifying variety (see Algedonic alerts in the viable system model or VSM). Beer's work in management cybernetics and VSM is largely based on variety engineering. Further applications involving Ashby's view of state counting include the analysis of digital bandwidth requirements, redundancy and software bloat, the bit representation of data types and indexes, analogue to digital conversion, the bounds on finite state machines and data compression. See also, e.g., Excited state, State (computer science), State pattern, State (controls) and Cellular automaton. Requisite Variety can be seen in Chaitin's Algorithmic information theory where a longer, higher variety program or finite state machine produces incompressible output with more variety or information content. In general a description of the required inputs and outputs is established then encoded with the minimum variety necessary. The mapping of input bits to output bits can then produce an estimate of the minimum hardware or software components necessary to produce the desired control behaviour; for example, in a piece of computer software or computer hardware. Variety is one of nine requisites that are required by an ethical regulator. See also Cardinality Complexity Degrees of freedom Power set Practopoiesis Waterbed theory Good regulator Ethical regulator State (Computer Science) Myhill-Nerode Theorem Space complexity Project Complexity References Further reading Ashby, W. R. 1956, An Introduction to Cybernetics, Chapman & Hall, 1956, (also available in electronic form as a PDF from Principia Cybernetica) Ashby, W. R. 1958, Requisite Variety and its implications for the control of complex systems, Cybernetica (Namur) Vol. 1, No. 2, 1958. Ashby, W. R. 1960, Design for a