Latest 3CX, Yealink T46G with latest firmware. I see the phones "go to sleep" after a few hours. The background image shows only; no line key labels. The phone is still registered; the BLF key LED's are still lit; when I push any physical button, the phone magically wakes up and the labels for the line keys appear again. It looks like some type of screen standby. What is this feature, and where is it in the default T46G template? I'd like to turn it off or at least adjust the timing of when it starts. TIA.