Labels like BN (Brown), BU (Blue), or G/Y (Green/Yellow) to identify physical wiring.
The phrase is a transliterated shorthand for "эл. схема подключения" (el. shema podkljucheniya), which translates from Russian/Ukrainian to "electrical connection diagram."
To find the specific diagram you need, it is best to include the and brand of the device you are working with. jel shema podkljuchenija kondicionera na | dec.risa.cx.ua
Wiring the indoor and outdoor units to the power grid.