Entertainment Computer System

The Entertainment Computer System (ECS) is an add-on peripheral released for the Intellivision video game console in 1983. It was Mattel Electronics' second attempt at creating a peripheral to upgrade the Intellivision into a home computer, and was rushed into production to appease the Federal Trade Commission after they began fining Mattel for false advertising following consumer complaints about the repeated delays in releasing the originally planned Intellivision Keyboard Component add-on.

Source: Wikipedia — Entertainment Computer System (CC BY-SA 4.0)