My answers to the following questions are based on the recording of the motorcycle with the stuck button using Channel 1, which was stuck for 5 and a half minutes. The link below plays the last 2:41 of this period.
https://mcadams.posc.mu.edu/dpdtapes/capture24.ramWhere do you hear the phrase "attention all units"?
This is very difficult to hear. Like the phrase “Hold everything secure”. But I here some brief phrase of “. . . all . . .” right at 2:00. But, admittedly, this is very difficult to make out.
Where do you hear "the sound of someone whistling"?
In several parts, but most clearly at 1:02, just after someone says “1 2 3 4”. It only lasts a couple of seconds, but is clearly a brief tune, not just a tone of some sort.
How does whistling indicate Trade Mart anyway?
It is a very strong indicator of a motorcycle not with the motorcade, not escorting the Presidential limousine at high speed to the Parkland Hospital.
If is a fairly strong indicator of a motorcycle at the Trade Mart Center because:
• It was known that several motorcycles were waiting at the Trade Mart Center.
• One can hear the sirens pass by the motorcycle making this recording and the Presidential limousine with the escorting motorcycles passed within 200 yards of the Trade Mart Center.
• An officer not actively escorting the President but waiting for him to arrive, might, in the few idle minutes left to him, and knowing nothing of the shooting, start to whistle.
But the bottom line, the whistling being recorded is wildly unlikely for Officer McLain’s motorcycle, just from the whistling alone.
How do you know the 2:41 excerpt was continuously recorded and is complete? I hear "clear 12:34" twice in the excerpt. Once at 2:23 and then again softer at about 2:32.
Because as long as the microphone button is stuck, it will keep recording continuously. It only stops recording if no one is transmitting anything. The phrase “clear 12:34” might be repeated twice in 9 seconds, in case the officer didn’t think his first message got through.