That box on your TV would have been a Nielsen box which sat on your TV and was connected to your landline. It didn’t collect anything automatically: every time you turned the TV on you were contractually obligated to press a button every 20 minutes to have the box call Nielsen and log a datapoint.
Those boxes have been phased out in favour of “Personal People Meters”[0], which are basically a pager with a SIM card that you wear which has a microphone listening 24/7 for TV broadcasts. You must keep it on you, listening at all times.
Nielsen will pay you $250/year (less than a dollar a day) for the data you provide.
Had them here in the UK, used to get a free TV license for the inconvenience. My mate always pressed the same button despite what channel we were watching though, so there is that...
Those boxes have been phased out in favour of “Personal People Meters”[0], which are basically a pager with a SIM card that you wear which has a microphone listening 24/7 for TV broadcasts. You must keep it on you, listening at all times.
Nielsen will pay you $250/year (less than a dollar a day) for the data you provide.
[0] https://en.wikipedia.org/wiki/Portable_People_Meter