Simplified explanation of Digital Signal in laymen's language?

Answer 1

To understand what a 'digital' signal is, it is important to know about signals and how we use them. Signals exist in order to communicate. It could be between two people, two machines, a radio station and an audience or countless other examples but communication by signals is the means. Communication is accomplished by creating signals in an agreed upon format, sending those signals, and completed by interpreting the signals created. There are many types of signals; semaphor is a visual communication system where the letters of the alphabet are represented by various positions of two visible flags. Morse Code again has the letters of the alphabet represented by sequences of electrically created dashes and dots. Spoken language is an audible signal of tones connected to establish words. Though there are many possible signals, in order to best understand what a 'digital' signal is lets focus on just two of the possible signals: Analog and Digital. Communication by telephone or radio began by creating analog signals. Even though one was through wire and the other through the airwaves, they both used signals referred to as analog signals. The first radio signals used a signal method called amplitude modulation or AM. AM created different sounds by increasing or decreasing the signal strength in an up and down sort of way. It worked pretty well but didn't go through thick walls made of concrete or metal. To overcome that limitation, FM was developed. Frequency Modulation is also an analog signal but instead of increasing or decreasing the signal strength, FM varies the sounds by pushing more or less signals at the receiver in a front to back sort of way. The first television was a mix of both FM and AM signals combined to give us both audio and the visual images. Our spoken language is an analog signal picked up by our ears through airwaves. Higher pitched sounds closely resemble an FM signal and louder sounds closely resemble an AM signal. So between two people who are talking and listening, they are doing so in an agreed upon format. The words that are spoken and listened to are the signals. The means of generating and interpreting those signals are done through a process of conversion. The process begins with the brain determining what it wants to communicate. That information goes to the larynx, lungs, lips, tongue and mouth and an converted into an audible signal. When that audible signal is received by the second person, the ear converts the signal into a format the brain understands and the communication is complete. If these two people could have communicated brain to brain, none of the signal conversion would have been necessary. Regardless of their lacking for brain to brain communication, that example illustrates that a signal conversion is often necessary in order for the means to either send or receive the communication. For those early inventors who brought us the first radio, telephone and television communications they did so by designing the means of taking audible sound and visual images and converting them into an analog signal. The analog signal was necessary because wire and radio, telephone & television equipment was the means that didn't understand any other signal other than analog signals. Right after those early inventors came more inventors who improved on their inventions with new inventions. More inventors followed and in fact have never stopped coming and improving previous inventions. Out of this non-stop cycle was born the 'digital'' signal as a means of taking amongst other things, an audible sound and visual image and converting them into a means that can be understood by another machine, ultimately converted into a sound or image we can understand. The signal of an analog device such as a radio, took a variable radio wave charge into the antenna. That charge was amplified into a higher and still variable voltage and through more amplifiers and filters was converted into sound waves emitted from the speaker that our ears would receive and be converted still again into a format our brain could dance to. The language of the computer is digital signal. Where an analog signal varied up and down for AM and more or less for FM, the digital signal was either on or off. The 1's and 0's of the computer device. Just as a device isn't limited to a radio or TV for an analog signal. Digital devices aren't just computers. So when you hear the term 'digital' you're hearing the means of how that device works. The language that it speaks and must be converted into and from in order to be understood. Devices that were designed using analog technology are extraordinary, beautiful things. For many years, there were things done by analog machines that could not be improved upon by digital machines. Television is a very good example of this and for most of the time television has been around, it has relied upon analog as the signal format. This format started with the broadcasters and ended with everyone's television sets. But as the new inventors and new inventions kept coming, the digital format earned its way into television technology. The first digital televisions were able to convert analog signals into digital signals and deliver the same picture and sound quality of the analog sets. Still new inventors and new inventions and now we have significantly improved picture quality but available only in a digital format. This is why we are seeing the change in signal format from analog to digital all the way from the broadcasters to our television sets. The broadcasters have largely converted over to sending out only digital signals and most televisions sold in recent years have been digital sets capable of converting analog signals. There are those sets still in operation that are pure analog which is the reason why they need to be connected to a digital converter box. There is certainly more that could be said about a digital signal however, at a high level seeing that it is a format used to communicate and that must be converted in order to be understood, may be a good start.