def _calculate_working_record_checksum(working_record):
    """
    Calculates the checksum of the argument ascii-hex string
    @retval int - modulo integer checksum value of argument ascii-hex string
    """
    checksum = 0

    # strip off the leading * and ID characters of the log line (3 characters) and
    # strip off the trailing Checksum characters (2 characters)
    star_and_checksum_stripped_working_record = working_record[3:-2]

    working_record_length = len(star_and_checksum_stripped_working_record)

    for x in range(0, working_record_length, 2):
        value = star_and_checksum_stripped_working_record[x:x+2]
        checksum += int(value, 16)

    modulo_checksum = checksum % 256

    return modulo_checksum