General Description1This product is a wireless transceiver, transmitting &receiving mode will automatically switched. to expressconveniently, in this user manual, it is called transmitter(master control unit) when being installed on the hotshoe of the camera, while it is called receiver (slave unit)when a flash is installed or connected.YN622C-TXLCD DisplayRecommended optional YN622C-TX E-TTLwireless flash controller as a transmitter,about the introduction of this product,please visit the following website :http://www.hkyongnuo.com/e-detaily.php?ID=348Off-CameraFlash622560-RXOFFYN622C IIOff-CameraFlashFlash Control Menu(Camera Menu)On-Top Flash