Some pretty handy items here...
Aerial Switches allow you to have one CB radio, and switch between two aerials, just by flicking a switch, or vice-versa, to switch two CB's on one aerial.
Invertors step up 12v to 240v so you can use mains powered items in your vehicle - ideal for low power consumption items like phone and handheld CB chargers, laptop power supplies, games consoles etc. Not suitable for heaters, TV's, kettles etc.
Droppers step down 24v electrical systems (as found in HGV's, some ex-military Land Rovers and some farm machines) to 12v so that standard 12v CB's (and car radios) can be used safely.