Tens of millions of Indian phones have gone dead, after the government blocked phones with no valid International Mobile Equipment Identity (IMEI) number.
The authorities are citing an increased threat from militants as the reason for the block.
The IMEI number is a 15-digit code which appears on the operators network when a call is made, and which allows calls and owners to be traced. Millions of phones lacking an IMEI number are in use in India, mostly cheap models imported from China.
Phones lacking the code were used in the planning of last year's attacks in Mumbai. There were calls at the time for a ban, with operators being given two months to ckeck IMEI numbers - a deadline which was extended several times.
The ban is believed to affect as many as 25 million phones. Users can contact their cellular operator to have an IMEI number installed at one of 2,000 centres across the country - but this doesn't look likely to be adequate in light of the enormous number of phones involved.
It'll probably do wonders for sales of cheap-but-legal phones in the country.