The documentation does not mention it but when the ECS Computer Adapter is used, "World Cup Soccer" can be played with one to four players, or two players cooperatively against the computer. In 1982 Mattel introduced a new peripheral for the Intellivision: the "Intellivoice Voice Synthesis Module". A speech synthesizer which produces speech with compatible cartridges. The Intellivoice was original in two respects: human sounding male and female voices with distinct accents, and the speech-supporting games were designed with speech being an integral part of the game-play. Like the Intellivision chip-set, the Intellivoice chip-set was developed by General Instrument. The SP0256-012 orator chip has 2KB ROM inside, and is used to store the speech for numerical digits, some common words, and the phrase "Mattel Electronics presents". Speech can also be processed from the Intellivoice's SP650 buffer chip, stored and loaded from cartridge memory. That buffer chip has its own I/O and the Intellivoice has a 30-pin expansion port under a removable top plate. Mattel Electronics planned to use that connector for wireless hand controllers. Mattel Electronics built a state of the art voice processing lab to produce the phrases used in Intellivoice games. However, the amount of speech that could be compressed into an 8K or 12K cartridge and still leave room for a game was limited. Intellivoice cartridges "Space Spartans" and "B-17 Bomber" did sell about 300,000 copies each, priced a few dollars more than regular Intellivision cartridges. However, at $79 the Intellivoice did not sell as well as Mattel expected, and Intellivoices were later offered free with the purchase of a Master Component. In August 1983 the Intellivoice system was quietly phased out. A children's title called "Magic Carousel", and foreign language versions of "Space Spartans" were completed but shelved. Additional games "Woody Woodpecker" and "Space Shuttle" went unfinished with the voice recordings unused. The four titles available for the Intellivoice system, in order of their release, were:   A fifth title, "Intellivision World Series Major League Baseball", developed as part of the Entertainment Computer System series, also supports the Intellivoice if both the ECS and Intellivoice are connected concurrently. Unlike the Intellivoice-specific games, however, "World Series Major League Baseball" is also playable without the Intellivoice module (but not without the ECS).