The prototype relay, like The Conduit, prototype relays can only send you to the 0.0 relay. They must be built with the arms on the east and west sides of the diamond block.
This is what a secondary relay looks like.
With the maintenance hatch open (it only opens when the core is missing) you can see the element zero core that powers the relay. Without this core, the relay will not send you anywhere, although it can still receive travelers.
What is that up in the sky? It's a mass relay!!!
This is the recipe for a probe. They come in sets of 5.
This is what a primary relay looks like.