Mobile communication allows people to communicate without physical connections using technologies like cellular networks. A cellular network uses radio transmitters and receivers in cells to connect mobile phones to each other and to wired telephone networks. The history of mobile phones began with two-way radios in the early 20th century, and modern cell phone networks were developed in the 1940s using cellular base stations. Global System for Mobile (GSM) is a second generation cellular standard that uses digital signals and has enabled many data applications on mobile phones.