Telecommunications refers to communication across a distance by means of various types of equipment. Visual signaling with flags, lamps, or smoke was the earliest form of telecommunication. Today, the term most often refers to a wide variety of electrical and electronic communication systems that transmit information throughout the world. This information may include sound, images, or text, or any combination of these elements. It may be in either analog or digital format. Analog information uses signals that are exact reproductions of the sound or picture being sent. It is transmitted in the form of a wave. Digital information is a numeric code that represents sound, images, or text.