- Teletran 3 is a computer in G.I. Joe vs. the Transformers continuity.
Teletran 3 is a supercomputer that forms the hub of Cybertron's transport network. It is capable of opening precision wormholes to physically connect two points, or smaller 'pinpoint' wormholes through which data can flow. Teletran 3 performs routine functions autonomously, but requires operator assistance to deal with new tasks.
Teletran 3 is capable of opening wormholes beyond Cybertron planetary space (such as on Earth), but it requires a wormhole generator on the far end to hold the gate open. During transport, Teletran 3 can filter a Transformer through a 'camouflage protocol,' reconfiguring their altmode to match the destination.
It is also capable of transporting objects through time- though this ability came as a surprise to all concerned, including Teletran 3. This method of time-travel is impractical for regular use because it has a significant chance of causing the Apocalypse.
Teletran 3 is sentient, possessing sufficient self-awareness to be embarrassed by the whole 'Apocalypse' thing, but it also appears indifferent to the Autobot/Decepticon conflict, serving whoever asks.
Please note 'Teletran 3' is actually spelled that way, unlike the various 'Teletraans' littering other continuities.
Though not explicitly stated, the wormhole network Teletran 3 commands is almost certainly the Space Bridge, which Optimus Prime later used to travel to Earth.
G.I. Joe vs. the Transformers Universe
G.I. Joe vs. the Transformers II
Shockwave arranged for the humans (specifically Cobra Commander) to discover technology to open a connection between Earth and Cybertron using Teletran 3's wormhole network. He planned to use this connection to invade Earth, enslave the populace, and steal its resources.
Instead a malfunction in the Earth gate caused Teletran 3 to overload, randomly transporting sixteen Cybertronians to different eras in Earth's past. Jazz, Bumblebee, Hot Rod, and Blitzwing were sent to the 1970s. Optimus Prime and the Stunticons were sent to 1937. Ratchet was sent to a post-apocalyptic future where Shockwave's invasion occoured as planned on on Hell Day, and the Dinobots were sent to the age of the Dinosaurs. If the missing Transformers were not retrieved, the resulting feedback would destroy all life on Earth. Perceptor used Teletran 3 to send G.I. Joe and Cobra members to retrieve them.
Shockwave attempted to prevent the last team from returning, reasoning that the ensuing destruction would render Earth fit for immediate strip-mining. This attempt was thwarted, and Shockwave was later overthrown when the Dinobots (rendered incredibly powerful by Teletran 3's reformatting them into dinosaurs) returned.
Optimus Prime made efforts to ensure that Teletran 3 could no longer open a wormhole to Earth, and advised humans to destroy all wormhole technology on Earth as well.