'apparatus for wireless telegraphy' means apparatus capable of emitting and receiving, or emitting only or receiving only, over paths which are not provided by any material substance constructed or arranged for that purpose, electric, magnetic or electro-magnetic energy, of a frequency not exceeding 3 million megahertz, whether or not such energy serves the conveying (whether they are actually received or not) of communications, sounds, signs, visual images or signals, or the actuation or control of machinery or apparatus, and includes any part of such apparatus, or any article capable of being used as part of such apparatus, and also includes any other apparatus which is associated with, or electrically coupled to, apparatus capable of so emitting such energy