Sir John Percival Vissing Madsen FAA (24 March 1879 – 4 October 1969) was an Australian academic, physicist, engineer, mathematician and Army officer. This history of JPVM's activities in Australian science & engineering covers the period 1900–1956 during which applications of electricity, X-ray analysis, standardised measurements for production, radio propagation, radar & radio astronomy, nuclear physics & digital computers made tremendous progress in part due to major advances in fundamental research & also the heightened activity due to two world wars. Central to these activities largely carried out at Sydney University, was the Electrical Engineering Department & the CSIRO National Standards Laboratory/ Radiophysics Laboratory (now The Madsen Building in the University grounds.