A sunset industry is an industry in decline, one that has passed its peak or boom periods. As one example, analogue

Analog signal

An analog or analogue signal is any continuous signal for which the time varying feature of the signal is a representation of some other time varying quantity, i.e., analogous to another time varying signal. It differs from a digital signal in terms of small fluctuations in the signal which are...

 recording technologies for audio or video have been surplanted by digital equivalents

Digital recording

In digital recording, digital audio and digital video is directly recorded to a storage device as a stream of discrete numbers, representing the changes in air pressure for audio and chroma and luminance values for video through time, thus making an abstract template for the original sound or...

; although analogue equipment is still offered, sales have declined dramatically and are not expected to recover, so this segment of the market has been branded a 'sunset industry'.