Historical overview of Equalization in Consumer Electronics

In the 1970s, the remaining picture quality limitations were concentrated in the transmission path, with multipath reflections the most challenging. Laboratory techniques to cancel the ghost images had surprisingly little benefit. What remained after substantial ghost reduction was still objectionable, unable to justify the high cost of the circuits. Simultaneously, the cable industry was rapidly penetrating the market, leaving few ghosts to cancel. So the effort was abandoned. Years later, interest in equalization again arose to aid transmitting data in the vertical blanking interval. In the digital environment, if the signal is improved sufficiently to distinguish "1s" from "0s", the data recovery could be near perfect. Unfortunately, teletext did not enjoy market acceptance in the US. Later, equalization became essential to the success of broadcast digital television. Currently, the excitement over mobile and portable applications promises to finally make equalization both mandatory and ubiquitous.