Canon's new Speedlite 600EX-RT is engineered to provide a new level of performance and reliability for professional flash photography with today's most advanced DSLRs. With wireless two-way radio communication, the Speedlite 600 EX-RT allows photographers to expand their creativity using wireless speedlites with the reliability of radio triggering. The Speedlite 600EX-RT offers an expanded zoom range and a higher guide number, plus a number of improvements over its predecessor in both operation and feel. It features a new dot-matrix LCD panel for display of all pertinent shooting information, backlit controls plus an internal sound generator. Reliability is ensured with improved hot shoe contacts, improved flash head durability and the most comprehensive dust and water sealing system ever on a Canon Speedlite flash. A new color filter holder helps maintain accurate color in a variety of ambient light conditions.
User guide can be found here: Manual