Speedlight is the brand name used by Nikon Corporation for their photographic flash units, used since the company's introduction of strobe flashes in the 1960s. Nikon's standalone Speedlights (those not built into the company's cameras) have the "SB-" prefix as part of their model designation. Current Speedlights and other Nikon accessories make up part of Nikon's "Creative Lighting System" (CLS), which includes the "Advanced Wireless Lighting", that enables various Nikon cameras to control multiple Nikon flash units in up to three separate controlled groups by sending encoded pre-flash signals to slave units.