[US] What is the start-of-packet marker ?

[brice]

As Santa Claus
I want to know the start-of-packet marker
So I can fix the communication device

Test data

        var testData = {
            /** message : position of start of packet marker */
            'mjqjpqmgbljsphdztnvjfqwrcgsmlb': 7,
            'bvwbjplbgvbhsrlpgdmjqwftvncz': 5,
            'nppdvjthqldpwncqszvftbrmjlhg': 6,
            'nznrnfrfntjfmvfwmzdfjlvtqnbhcprsg': 10,
            'zcfzfwzzqfrljwzlrfnpqdbhtmscgvjw': 11
        };