bt1_off = new Image(290, 20);
bt1_off.src = "images/bt1.gif";
bt1_on = new Image(290, 20);
bt1_on.src = "images/bt1_on.gif";

bt2_off = new Image(290, 20);
bt2_off.src = "images/bt2.gif";
bt2_on = new Image(290, 20);
bt2_on.src = "images/bt2_on.gif";

bt3_off = new Image(290, 20);
bt3_off.src = "images/bt3.gif";
bt3_on = new Image(290, 20);
bt3_on.src = "images/bt3_on.gif";

bt4_off = new Image(290, 20);
bt4_off.src = "images/bt4.gif";
bt4_on = new Image(290, 20);
bt4_on.src = "images/bt4_on.gif";

bt5_off = new Image(290, 20);
bt5_off.src = "images/bt5.gif";
bt5_on = new Image(290, 20);
bt5_on.src = "images/bt5_on.gif";

bt6_off = new Image(290, 20);
bt6_off.src = "images/bt6.gif";
bt6_on = new Image(290, 20);
bt6_on.src = "images/bt6_on.gif";

bt7_off = new Image(290, 20);
bt7_off.src = "images/bt7.gif";
bt7_on = new Image(290, 20);
bt7_on.src = "images/bt7_on.gif";

bt8_off = new Image(290, 20);
bt8_off.src = "images/bt8.gif";
bt8_on = new Image(290, 20);
bt8_on.src = "images/bt8_on.gif";



function on(n)
{
	 btName = 'bt'+n;
     document.images[btName].src = eval(btName + "_on" + ".src");
}

function off(n)
{
	 btName = 'bt'+n;
     document.images[btName].src = eval(btName + "_off" + ".src");
}