Mobile phone commercially available handheld mobile phone. From 1983 to 2014, worldwide mobile phone subscriptions grew to over seven billion—enough to provide one for every person on Earth. In first quarter of 2016, the top smartphone developers worldwide were Samsung, Apple, and Huawei, with smartphone sales represented 78 percent of total mobile phone sales. For feature phones (or "dumbphones") , the largest were Samsung, Nokia, and Alcatel. A handheld mobile radio telephone service was envisioned in the early stages of radio engineering. In 1917, Finnish inventor Eric Tigerstedt filed a patent for a "pocket-size folding telephone with a very thin carbon microphone".
Mobile phone signal call to be "dropped" is if the mobile phone subscriber travels outside the coverage area—the cellular network radio tower(s). After a telephone connection between two subscribers has been completed, it must remain within range of that subscribers network provider or that connection will lost (dropped). Not all cellular telephone radio towers are owned by the same telephone company (though this is not true to all locations) be maintained across a different company's network (as calls cannot be re-routed over the traditional phone network while in progress), also resulting in the termination of the call once a signal cannot be maintained