Insulator
The insulator can be used to extend wire connection lines by providing another connection point for them.
When used in conjunction with the Copper Wire, the wire will be connected to the insulator, after which it can be connected to either another insulator, or some other wire-connecting block.
Core Extension
The insulator can be used in order to extend the core of an Antenna, so that you can place Transmitters and Receivers farther away from them.