With reference to games consoles
, a device that allows cartridges or discs from one territory
to play on a console from another. Eg, playing a Japanese game on a UK SNES
. For cartridge based consoles, the adaptor fits between the console and the cartridge, in some cases (eg, SNES) requiring a second cartridge to present the console with local key. Sold in import shops. In disc based systems, the adapter plugs into an expansion slot on the console.
A quick explaination of why these things exist: The console manufacturers in Japan, instead of distributing their consoles and games themselves in other countries, form subsidiary companies or licence the distribution rights to third parties. Since a second company is then involved, competition between the parent company and the subsidiary or licencee is undesirable. However, because games generally come out in Japan before elsewhere in the world, people import the games, taking money away from the local company. This is why consoles are built with territorial lockouts.
Sometimes the lockout takes the form of a software check that tests the state of jumpers or reads the teritory from a ROM. This can be also be defeated using a teritory switch. Other times, the lockout is a hardware device in the console that will refuse to allow the console to boot if it isn't presented with the correct key in the cartridge or code on the disc. These can also be defeated using a lockout bypass or mod chip. For the PC Engine / Turbo Grafx 16, the pins on the Japanese and US cards are in a different order. There's a switch that can be installed for this too, but it's a lot of hassle.
Any SNES gamer who has been buying import games since the console's birth will tell you of the constant ongoing battle between the games companies and adaptor manufacturers that raged during 1992 and 93. At one point, it was necessary to buy a new adaptor for every new game, as the developers devised new methods of detecting a territory mismatch, and new developments like the Super FX chip were brought out. The Fire FX adaptor seems to work well for most games though.
See also: bridge adaptor, adaptor damage, lockout bypass, mod cartridge.