Mobile carriers might have to write off as much as 70 per cent of their equipment when moving from second- to third-generation mobile networks in the next few years, an industry official has warned. 'How much of the equipment that you buy now can still be used by 2005 and how much will you have to put in the bin?' Ian Goetz, marketing director in the mobile segment of British mobile networking solutions developer Tellabs, said at the International Telecommunication Union's Telecom Asia 2002 in Hong Kong yesterday. Companies were warned of the hidden costs they could bear when deploying 3G networks before investing billions of dollars. He said nearly three-quarters of 2G equipment would be wasted. Mr Goetz also said since more than 90 per cent of the mobile traffic involved voice rather than data, companies would have to solve the problem of carrying voice communications between 2G and 3G networks. The industry must draw on past lessons, he said, pointing out how handset development had lagged other technologies. GSM handsets came out a year after the technology became available.