[Jmenschenfresser]

Long range scanners give you the ability to see what's on the inside of ships (weapons, armor, etc). There is a scanner jammer that blocks this.

Mount window button can be found on the top right of the design screen (once you have started to design your ship, base or whatever)

In the stock game all the different scanners do the same thing--give the ability to detect cloaked ships at different levels of cloaking. However since they've given us something like five different types of cloaking (temporal, active, passive, blah blah blah), it would be possible to make different devices which require different scanners. Or something like that.