Asterisk, Cisco 7970 and standby mode


I setup Cisco 7970 phones under Asterisk successfully. They work fine. Except one problem. Their screens aren’t switched off if phone is not used. I tried to add to the phone XML config file daysBacklightNotActive and
daysDisplayNotActive options but without any luck.

Can somebody give me a right point to solve this problem?

Thanks in advance.