We saw in an earlier post how the military uses communication headsets with red LEDs in the tips of the antennas that provide a social signal about the attention of its wearer. On board the spaceship to Fhloston Paradise, the same technique is used to signal functioning microphones.
The simple status signal of glowing signals to the speaker that the device is on and that their voice is being broadcast, listened to, or might be overheard.
These are two binary states: microphone recording/not, light on/off. and the relationship could be swapped such that the light illuminates when the device is not recording. But since the consequences for accidentally broadcasting the wrong thing are dire, it makes sense to associate the attention-getting signal with the costly state that requires attention and care.
The red appears elsewhere as a signal for microphone or antenna, even when it’s not glowing. We see it on Korben’s wireless phone at home, Zorg’s assistant’s headset, on Korben’s room phone aboard the Fhloston Paradise, on the handheld mic aboard Zorg’s ship, and on the President’s wireless phone. We can presume it’s a signal common pattern across all the commucication technology of this world. The commonality helps signal to anyone familiar with it the purpose of an otherwise unmarked and miniaturized component.