Defining Characteristics of Cross-Sectional Studies. Think of a cross-sectional study as a snapshot of a particular group of people at a given point in time. Unlike longitudinal studies that look at a group of people over an extended period, cross-sectional studies are used to describe what is happening at the present moment.
Dec. 3, 1992: The first text message Papworth, a former developer at Sema Group Telecoms, sends the world's first SMS greeting to his friend Richard Jarvis, who at the time worked at U.K. service Vodafone. Jarvis couldn't say Merry Christmas back, because his brick-sized Orbitel 901 phone had no way of inputting text.
DTMF was known throughout the Bell System by the trademark Touch-Tone. The term was first used by AT&T in commerce on July 5, 1960 and was introduced to the public on November 18, 1963, when the first push-button telephone was made available to the public.