function clear_field(field) {
		if (field.value==field.defaultValue) {
			field.value=''
		}
	}


function calculatePIatt()
{
   var Rohm  = parseFloat(document.attPI.Rohm.value);
   var attenuation  = parseFloat(document.attPI.attenuation.value);

   var  R1ohm = (Rohm * ((attenuation + 1)/(attenuation - 1)));
   var  R2ohm = ((Rohm / 2)*((Math.pow(attenuation, 2) - 1)/attenuation));
   var  attendb = (20 * (Math.log(attenuation) / Math.log(10)));

   document.attPI.R1ohm.value  = R1ohm.toFixed(2);
   document.attPI.R2ohm.value  = R2ohm.toFixed(2);
   document.attPI.attendb.value  = attendb.toFixed(4);


   return;
}


function calculateTatt()
{
   var Rohm  = parseFloat(document.attT.Rohm.value);
   var attenuation  = parseFloat(document.attT.attenuation.value);

   var  R3ohm = (Rohm * ((attenuation - 1)/(attenuation + 1)));
   var  R4ohm = 2 * Rohm /(attenuation - 1/attenuation);
   var  attendb = (20 * (Math.log(attenuation) / Math.log(10)));

   document.attT.R3ohm.value  = R3ohm.toFixed(2);
   document.attT.R4ohm.value  = R4ohm.toFixed(2);
   document.attT.attendb.value  = attendb.toFixed(4);


   return;
}