Forgive me if this has been covered or is obvious.
I get signals through completing missions (and so on), and in crates, but when I go to the exterior tab to mount them, they come with a cost. However, in my inventory I see many there that I can sell.
I realise there is a top layer of free signals, so they are not in question, it's the second layer I'm confused about.
So what am I missing? Do I only pay once to mount a signal from the second layer, then they are resupplied free (from my stock) or will I pay each time they are resupplied?
Thanks for any help offered.....