Analog television or analogue television is the original television technology that used analog signals to transmit video and audio. In an analog television broadcast, the brightness, colors and sound are represented by rapid variations of either the amplitude, frequency or phase of the signal.Analog signals vary over a continuous range of possible values which means that electronic noise and interference becomes reproduced by the receiver. So with analog, a moderately weak signal becomes snowy and subject to interference. In contrast, a moderately weak digital signal and a very strong digital signal transmit equal picture quality. Analog television may be wireless or can be distributed over a cable network using cable converters.All broadcast television systems preceding digital transmission of digital television (DTV) used analog signals.Analog television around the world has been in the process of shutting down since the late 2000s and is expected to be completely replaced by digital television by 2021.