currentImage = "1";

function switchPort(newImage)
{
	
	document['port'+currentImage].src = 'images/'+currentImage+'1.gif';
	document['port'+newImage].src = 'images/'+newImage+'2.gif';
	
	// load the new image
	document.port_pict.src = 'images/port'+newImage+'.jpg';
	currentImage = newImage;
}