These are older 'truck toyz'.  Many different sounds were produced and sold for use with the RF Limited "The Agitator" Control box, DS-2040, and the DS-2039 Digitally Synthesized CB Microphone.  You could even have your own personal message programmed for it. 

• Plugs into either the Control Box or the microphone
• View from both sides
• Titled 18 WHEELER
• Great item for collectors