When uninterruptible power supplies (UPS) were developed for the oil and emerging computer industries in the 1950s their primary purpose was to provide both ‘uninterruptible power’ and condition the power which could be mains derived or supplied by a local generating set. Early computer power supplies where less reliable than they are today, with smaller input voltage and frequency windows and were very susceptible to power pollution: sags, surges, brownouts, spikes, transients and electrical noise.
