I remember a time when late at night (maybe around 12:30 or 1:00) that pretty much every channel would play the national anthem accompanied by patriotic images and then cut to a test pattern until around 6:00 or 6:30 AM when programming would resume. No infomercials all hours of the night in the 70's. Kids today will never know the glory of "The Test Pattern".
Ahh yes indeed! Time to shut off the idiot box. That was the real signal for bedtime. Sometimes, we could stay up late and night, long into the silence of static when the rest of the world was quiet and play with our 300-baud modems.