is a serious risk that must be carefully assessed. History The first patent for phase-fired controllers derives from 1912. However realization was first possible in the 1920s when mercury-arc valve rectifiers with control grids became available. However, this method of voltage regulation was not common at the time, because of the limitations of mercury arc valves. It became widespread with the invention of solid-state thyristors at the end of the 1950s. See also Burst-fired controllers References Telecommunication theory Radio modulation modes Physical layer protocols Data transmission