"SYSTEM HAS THREE MAIN CABLES THAT INTERFACE TO THE TANK'S FIRE CONTORL & POWER SYSTEM. THE FUNCTIONAL TEST UNIT CONNECTS TO THESE CABLES FOR A SYSTEM TEST, OR INDIVIDUALLY TO TROUBLE SHOOT THE CABLE & DEVICES CONNECTED TO IT. THE FUNCTIONAL TEST UNIT UTILIZES A 5V & 28V POWER SUPPLY, SIMPLE MECHANICAL SWITCHES (A ROTARY & 9 PUSHBUTTON), INDICATORS & A TRIGGER CIRCUIT TO DEVELOP A 0.100MS PULSE"