At first I'd like to thanks @Mito. He knows why. There is a lot of members of our community who has problems with RCU (batteries, not working buttons, ...) It's very simple to check it. HowTo Check RCU in Very Simple Way. 1. Use your digital camera, smartphone, webcam, ... 2. Point your RCU to your camera lens, look at LCD device display. 3. If your RCU IR transmitter is working well, you should see white/violet light of IR LED on your display after pressing RCU buttons. 4. If you can't see nothing or very low intensity of light, change batteries at first. That's it . I hope, will be useful for all. PS: Sorry for bad photo.