@staticmethod
def request_output_status(output_id):
    """Generate an output-port status request.

        :param    int    output_id:    Output id 0..3
        :return:    The PCK command (without address header) as text
        :rtype:    str
        """
    if output_id < 0 or output_id > 3:
        raise ValueError('Invalid output_id.')
    return 'SMA{:d}'.format(output_id + 1)
