It's a circuit that alerts people to dead carriers.
People in radio station studios generally don't listen to the over-the-air signal because there is a delay. A silence sense is a circuit that monitors the over-the-air signal and takes action when it's been too quiet for too long. This is usually an indication that something has failed, either at the transmitter, or in the studio-transmitter link. It is sometimes triggered by dramatic pauses in classical music and talk show content, but in those cases is ignored by the DJ/host/producer.
They've been around forever, and can be made from simple analog circuits. In the stations where I've worked, if the silence sense activated, a red light lit up in the DJ booth, and the engineering department. Some stations had a secondary silence sense that would wait a bit longer, and light up a light bulb at the receptionist's desk because she had the master list of phone numbers to call the right people in case of a transmission failure.
There are thousands of radio station transmitters that are far enough away from the originating studio that it's not possible for the studio to hear the over-the-air signal, so a silence sense on top of a mountain, next to the transmitter could send an alert packet via this satellite service back to the studio to let someone know something is wrong.
This service is high latency at present and only supports sending uplink data a half-dozen times per day when satellites are overhead. It would likely not be suitable for this application.
I'm speculating, but certain FCC licenses require you to transmit without significant gaps on your licensed frequencies or be fined. (The theory being that others could be making better use of your frequency since you aren't using it.) If your transmission gear goes down for whatever reason, you want to notify the FCC before others do. E.g.,
