system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: During the Apollo missions, what is the purpose of the "beep" you hear regularly in the background?

At first I thought it was maybe something marking the passing of time, but the beep seems to happen in an irregular pattern.  It also doesn't seem to correspond to when people start talking, so what could it be?
gpt
They are called Quindar tones and they served to turn the transmitter on and off such as with push-to-talk. The issue is that to keep track of the astronauts from a rotating Earth required a worldwide network and frequent switching between transmitters and receivers. The tones mediated all that, so they should in general follow when people are talking.