Just position the digital reader over print and take a picture. In only seconds, the device’s synthetic voice reads the printed message. The National Federation of the Blind plans to put the device on sale Saturday, when its annual meeting gets under way in Dallas. The device, combining a personal digital assistant and a digital camera, was developed by inventor Ray Kurzweil and the membership organization of more than 50,000 blind people. It’s been dubbed the Kurzweil-National Federation of the Blind Reader.