// imgArray holds all on images followed by off images	
	imgArray = new Array();
	
	
// 'on' images
	imgArray[0] = new Image();
	imgArray[0].src = './images/instruments-1.gif';
	imgArray[2] = new Image();
	imgArray[2].src = './images/customers-1.gif';
	imgArray[3] = new Image();
	imgArray[3].src = './images/about-us-1.gif';
	imgArray[4] = new Image();
	imgArray[4].src = './images/contact-1.gif';
	imgArray[5] = new Image();
	imgArray[5].src = './images/home-1.gif';
		
			
// 'off' images
	imgArray[6] = new Image();
	imgArray[6].src = './images/instruments.gif';
	imgArray[8] = new Image();
	imgArray[8].src = './images/customers.gif';
	imgArray[9] = new Image();
	imgArray[9].src = './images/about-us.gif';
	imgArray[10] = new Image();
	imgArray[10].src = './images/contact.gif';
	imgArray[11] = new Image();
	imgArray[11].src = './images/home.gif';
		

/*
	Function to swap images ... uses imgArray[]
*/
	function swap( imgNum, action )	{
		var num_img = (action=='on') ? imgNum : imgNum+6;
		// . add number of images preceding first button
		document.images[imgNum].src = imgArray[num_img].src;
		
	}