Sprint announced its first dual-mode device that lets subscribers connect over both 3G and 4G WiMAX networks. The Sprint 3G/4G USB Modem U300, manufactured by Franklin Wireless, is a USB modem that can achieve download speeds of 2 to 4 Mbps within WiMAX range, and downlink speeds of 600 Kbps to 1.4 Mbps when connected to Sprint's 3G (EV-DO Rev A) network.

The U300 works with Windows Vista and XP along with Sprint Connection Manager, which automatically determines the fastest connection available in any given location and uses that (similar to how today's 3G devices roll back to 2G whenever necessary).

Sprint launched its 4G network in Baltimore back in September. The carrier still plans to flip the switch in other cities over the course of 2009, although its rollout schedule is still somewhat vague at this point.

The Sprint 3G/4G USB Modem U300 lists for $149.99 with a two-year contract and after a $50 mail-in rebate. The 3G/4G hybrid plan costs $79.99 per month ($20 more than a regular 3G or 4G broadband plan on Sprint). Look for it in stores on December 21st. For more information, visit www.sprint.com/4g.