Carriers` transition to VoIP may not begin in earnest until 2010, though spending on gear for the technology will roughly double over the next five years, according to research company  Dell`Oro Group. Network equipment providers sold about US$2.4 billion worth of dedicated VoIP infrastructure products in 2005, a number that will grow to $4.7 billion by 2010, according to Steve Raab, an analyst at Dell`Oro. The company counted softswitches (servers that switch packet-based calls), media gateways (devices that translate between packet and circuit-switched networks) and products that combine those elements, Raab said. It did not include VoIP elements built into other products such as multiservice switches.