AT&T is one of the largest communications holding companies in the United States. It is a global provider of Internet protocol-based communications services to businesses. It also provides wireless, high-speed Internet access, local and long-distance voice, directory publishing and advertising services. The company serves more than 60 million customers worldwide. It publishes more than 175 million directories every year. The company offers a variety of devices that connect to customers' office applications and serves critical business needs in a mobile environment. It offers enhanced data phones, mobile smartphones, laptop modem cards and specialized devices. The company has a patented network, ALLOVER, which provides customers with a global system for mobile communication and general packet radio service.