Suddenly, Buzz and Neil heard the high-pitched sound of the Master Alarm. On the computer display the “PROG” light glowed amber. “Program alarm,” Armstrong radioed. Quickly, Aldrin queried the computer for the alarm code, and “1202” flashed on the display.
The machine-like performance of flight crew and ground controllers continued. Each participant was in perfect harmony with the other, moving to a cadence dictated by the laws of physics and the clock.
As they passed behind the moon, they had just over 8 minutes to go before the burn. They were super-careful now, they checked and rechecked each step several times. It had to be perfect. Just one digit in the computer out of place could send them into a lunar mountain or turn them and send them into orbit around the sun.