This is essentially a rudimentary audio control and volume adjustment panel. Each pilot has their own subscriber panel which is used to enable/disable audio sources and adjust their volume. The control functions are listed below:
СПУ (SPU): Intercom System
РАД (RAD): Radio
РЕЗ (REZ): Reserve/Backup
РК (RK): Radio Compass/Direction Finder

This is just a basic plastic enclosure with no active circuitry contained within.

There is a permanently attached wire harness along with a 15-pin connector on the back, which looks like the soviet equivalent of a D-SUB connector. The back metal plate is secured to the casing by some slotted screws.

We found the pins for the backlight and applied 28V to light up the panel. It is lit by a single incandescent bulb located in a socket in the center of the panel.

Removing the illuminated faceplate reveals the bulb socket and switch retention screws.

There's not much to see inside this panel, just some wiring and the back of the switches and potentiometers.