Sg-1000 (stands for "Sega Game 1000") is a cartridge-based videogame console.
In July 1983, Sega released the SG-1000 in Japan, then was sold in Asia, New Zealand, Italy, Spain and South Africa. An SG-1000 clone manufactured by Tsukada Original is called "Othello Multivision", and the "Telegames Personal Arcade" is a console by Telegames which can run SG-1000 and Colecovision games.
In July 1984, Sega released an updated version of the SG-1000 that was called SG-1000 Mark II, included an optional keyboard and an optional game card reader add-on called the Card Catcher.
A computer version of this console, with a built-in keyboard, was released as SC-3000, who had an add-on called the SF-7000 which added 64KB of RAM, 8KB ROM and a 3-inch floppy disk drive.
In October 1985, Sega released the SG-1000 Mark III with improved video hardware and more RAM, and the card reader was built-in.
The famous Sega Master System is just a redesigned Sega SG-1000 Mark III. SG-1000 card games are compatibles with the Master System I.