Repeaters - huge structures by Reapers, scattered across the galaxy who can create something like a corridor, where the body does not have the weight that allows instantaneous travel distances, to overcome that with conventional SSD would have taken years or even centuries.
Primary repeaters can make moving ships thousands of light years, from one arm of the galaxy to the other. However, each relay has a fixed primary message with just one in the same and can perform the movement of ships only to him. Secondary relays can perform the movement of ships for a few hundred light years and have no fixed posts, any secondary repeater can perform the movement of ships to any relay, located within a radius of its action
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