In modern times, this means sending information between machines which are connected together using electrical, optical, or radio signals. There are FOUR basic elements involved in communication.
Digital signals are the language of modern day computers.
Digital signals comprise only two states. Digital signals require greater bandwidth capacity than analog signals, thus are more expensive to communicate. The following diagram shows a digital signal. A digital 0-bit is usually measured as a 0v signal. Digital signals are also called square waves .