Work on HD-MAC specification started officially in May 1986. The purpose was to react against a Japanese proposal, supported by the US, which aimed to establish the NHK-designed Hi-vision system as a world standard. Besides preservation of the European electronic industry, there was also a need to produce a standard that would be compliant with the 50 Hz field frequency systems (used by a large majority of countries in the world). Truth be said, the precisely 60 Hz of the Japanese proposal was also worrying the US, as their NTSC M-based standard definition infrastructure used a practical frequency of 59.94 Hz. This apparently minor difference had the potential for a lot of trouble.