The Intellivision is a video game console released by Mattel in 1979.

Like Atari, Mattel marketed their console to a number of retailers as a rebadged unit. These models include the Radio Shack TandyVision, the GTE-Sylvania Intellivision, and the Sears Super Video Arcade. The Sears model was a specific coup for Mattel, as Sears was already selling a rebadged Atari 2600 unit, and in doing so made a big contribution to Atari's success.

Mattel emulated rival Coleco in more ways than one - they promised a "Keyboard Component System" which would turn the Intellivision into a home computer.  After many delays, although 4,000 units were made, it is unclear how many reached consumers and Mattel fell foul of the Federal Trade Commission by not delivering its advertised claim and as part of the settlement, in 1982, had to write and recall the few units which had been shipped.
Eventually Mattel scrapped that project and offered a simpler upgrade - the "Entertainment Computer System", which offered a simple BASIC, 2K extra RAM and a much simplified cassette and thermal printer interface.

The other main upgrade for the system, was the release of the Intellivoice -  voice synthesiser system which produced speed with four games titles:
Space Spartans, Bomb Squad, B-17 Bomber and Ton: Solar Sailer (which all require the Intellivoice to work).  Intellivision World Series Major League Baseball was also released for the Entertainment Computer System which would work with Intellivoice if present.

1983 also saw the release of the improved Intellivision II which could play Atari 2600 games with a system changer module.  Alas some of the earlier games will not work with this version of the system.

The Intellivison proved popular with over 2 million consoles sold by 1982, and with the best selling games selling over 1 million copies.  Less than a dozen software titles were released for the Entertainment Computer System.

The rights and stock were eventually purchased by INTV Corp, who released their own games consoles based on the Intellivision.