Wireless flash capability was introduced with the DYNAX 7xi in 1991. The capability is included with most Minolta DYNAX cameras. With DYNAX cameras having built-in flashes, the built-in flash is used as a signal sender to start and stop wireless controlled off-camera flash. Pressing the flash control button on these cameras will also use the built-in flash as part of a 2:1 ratio flash exposure. When properly activated and the shutter release button is pressed to take a picture, the built in flash will emit a low-power, coded white-light pulse which is keyed to the off-camera flash (for channel 1-4). Upon "seeing" the properly coded pulse from the camera, the flash will emit a rapidly pulsed flash. Each flash pulse passes through the camera lens, is refleced off the film and read by the camera’s TTL flash system. The flash continues to pulse and the accumulated exposure is measured. When enough flash pulses reach the film to produce a proper exposure, the camera’s built-in flash is directed to fire another coded burst to stop the firing of the wireless, off-camera flash. It is possible to use many Minolta 3500xi, 5400xi/HS, 3600HS(D), 5600HS(D) flash units together for lighting large areas or dimensional lighting (digital cameras: only D-flashes are supported). As this is a low-power, pulse-light system, it is not possible to use any other flash units with Minolta wireless flash units. New technology developments of the Dynax 7 system enable high-speed wireless flash photography at up to 1/200 second. To obtain this level, the camera must be use with a Dynax (D) lens and either 3600HS(D) or 5600HS(D) flash.