There was a great research on that in USSR around at the same time, 1975, when schcema was created.
https://www.youtube.com/watch?v=dgHseIp1YZg&list=PLOWNkHTFkkpPTMvLPxZG8BOiydK0H0iTu&index=31&pp=iAQB0gcJCQMKAYcqIYzv
An attached document is inside.
Прояв - is a display.
It is a bit engaged.
This answer is not deleted, so it is not even a red flag.