if(document.images) 
{    
  m1_on = new Image;
  m1_on.src = 'images/m1_on.png';
  m1_off = new Image;
  m1_off.src = 'images/m1_off.png';     

  m2_on = new Image;
  m2_on.src = 'images/m2_on.png';
  m2_off = new Image;
  m2_off.src = 'images/m2_off.png';     

  m3_on = new Image;
  m3_on.src = 'images/m3_on.png';
  m3_off = new Image;
  m3_off.src = 'images/m3_off.png';     

  m4_on = new Image;
  m4_on.src = 'images/m4_on.png';
  m4_off = new Image;
  m4_off.src = 'images/m4_off.png';     

  m5_on = new Image;
  m5_on.src = 'images/m5_on.png';
  m5_off = new Image;
  m5_off.src = 'images/m5_off.png';     

  m6_on = new Image;
  m6_on.src = 'images/m6_on.png';
  m6_off = new Image;
  m6_off.src = 'images/m6_off.png';     
 

}

function imgAct(img_name)
{
  if(document.images) {
    img_on = eval(img_name + '_on.src');      
	document.getElementById(img_name).src = img_on;
  }
}

function imgInact(img_name)
{
  if(document.images) {
    img_off = eval(img_name + '_off.src');          
    document.getElementById(img_name).src = img_off;
  }
}