The XBee-PRO XTC Module from Digi is a RF module that operates from 902 to 928 MHz in the ISM band. Its output power is software adjustable from 100 mW to 1 W - the maximum output power allowable by governments that use 900 MHz as a license-free band. This high power gives it an outdoor line of sight range of up to 40 miles (64 km) with a high gain antenna & up to 14 miles (22 km) with a 2.1 dB dipole antenna. The module has a receiver sensitivity of -110 dBm. It uses FHSS (Frequency Hopping Spread Spectrum) agility to avoid interference by hopping to a new frequency on every packet transmission or re-transmission. The module is approved for use in the United States, Canada, Australia and other countries. They are available in XTend and XBee SMT form factor.