China's cyberspace regulator said on Wednesday children under the age of 18 should be limited to a maximum of two hours a day on their smartphones, sending shares in tech companies tumbling. The Cyberspace Administration of China (CAC) said it wanted providers of smart devices to introduce so-called minor mode programmes that would bar users under 18 from accessing the internet on mobile devices from 10 p.m. to 6 a.m. Users aged 16 to 18 would be allowed two hours a day, children aged eight to 16 would get one hour while children under eight would be allowed just eight minutes.