When I was a student, watching TV late at night in the college TV room, it was the done thing so stay up until the channels all shut down, played the national anthem, showed the test card, whistled for a bit and then shut down completely. Watching the picture slowly shrink and disappear into a little white dot in the centre of the screen was generally the signal to go to bed. Or check if the bar was still open...
I remember the BBC one having a little girl in the centre circle drawing on a blackboard
I think the Test Card was accompanied by music and the high pitched whistle accompanied a grey fizzing screen when no picture was transmitted at all
I remember the late night sign-offs, particularly fighter jets flying overhead while the national anthem played.
Here's a guy who made a website aggregating a broad collection of various sign-offs from TV stations across the U.S. -- http://www.tv-signoffs.com/
these test patterns were sent to test overall performance of the video communication systems.Nowadays we do not receive these test patterns and we do not know how good is our televisions with respect to linearity,picture size,aspect ratio,bandwidth etc.
I have an American test pattern board in my closet from when we were doing amateur tv in the Bronx NYC in the 70's those were the days. 7 tv stations, off at midnight with Quality programming. The old saying when they has mystery programs on the radio, radio is for people with minds, TV is for people who are mindless. You could close your eyes listening to some programs on the radio and envision the whole scenario. not any more ....
In North America we had the "Indian Head" test pattern seen here
The circle allowed TV receiver adjustments of vertical height and linearity, the better TVs had separate linearity controls for the top and bottom of the screen. Some even had horizontal width adjustment. With the advent of colour TV the shop convergence test generator replaced this broadcast test pattern.
I remember the Canadian national anthem at the beginning of every Saturday afternoon cinema, we all stood proudly to watch the coast-to-coast flyover. Then the newsreel, cartoon, serial, finally the movie.
When we eventually moved to an area that had broadcast TV available there were only 2 English channels (CBC and CTV), the French CBC, and a snowy channel from just over the USA border. One needed a high mast and high gain rooftop antenna for the American station and had to have the good fortune of no metallic structures in the line of sight.
And remember how an aircraft flying overhead or a Ford going down the street would raise all sorts of havoc with the reception?
Depending on the channel, our stations would stop broadcasting some time from 10:00pm (for PBS) to midnight or perhaps 2:00am. The stations would typically play the national anthem. We wouldn't stand though. I think you only do that in public in America. After the anthem some channels would go to the test pattern and others to static. I recall what looked more like an electronically generated pattern than a physical card.
On weekends some of the stations would stay on later playing such SciFi classics as "Them", "The Day The Earth Stood Still" and "The Monolith Monsters."
I think the stations typically started broadcasting again at 5:00 or 6:00am, but I wasn't up that early to know for sure.