Quindar tones are like musical beeps that were used during the time of the Apollo missions to space. They were sent over the radio system to help NASA control the communication between the astronauts and the ground team.
Just like how the beep of a car horn or a doorbell has a specific sound, quindar tones have their own unique sound too. They were used to signal the beginning and end of a message between the astronauts and the control team. Think of them like musical notes that help people talk to each other even when they're really far away!
The two sounds of the quindar tone were one very high pitched beep and one lower pitched beep. The high pitched beep was used to signal the start of a message, and the lower pitched beep was used to signal the end of a message.
Even though quindar tones are not used as much today, they are still an important part of the history of space exploration. They helped astronauts talk to NASA back on Earth, which was a huge accomplishment at the time!