Line busy indicator

Hi everyone. I’m using Asterisk in 5 offices now and I just want to start off by saying it’s awesome. I’ve been managing it for almost 3 years and am blown away by all the stuff it can do. So thanks.

I’m using a Polycom soundpoint IP 601 in a couple of offices. I go with Polycoms because they boast how great they work with Asterisk. Anyway, next to the speed dial numbers, there is a Line Busy Indicator Light that should light up solid if that person is on the phone. I have never been able to get this feature to work. The Asterisk servers are on PRI and call waiting is enabled if that matters. My question is this. Is there an option in say sip.conf or wherever that must be enabled for this feature to work? Any insight to this is greatly appreciated. Thanks everyone.