public String mode_string()
	{
	   switch (h_mode)
	   {
	     case STEREO:
	  	return "Stereo";
	     case JOINT_STEREO:
	  	return "Joint stereo";
	     case DUAL_CHANNEL:
	  	return "Dual channel";
	     case SINGLE_CHANNEL:
	  	return "Single channel";
	   }
	   return null;
	}