Cisco 7931: Getting Your New IP Phone System To Act Like The Old PBX Style Systems

I have a customer that wanted the new Cisco system to work like a PBX.  They wanted to know when someone was on the phone by looking at a 'light' by their extension, very much like the old school phones.  Sounds like the old PBX to me.  Or, Presence is always an option, but thats only if the have decent computers, which this client doesnt.  However, you can do it easily with the 7931 phone.   Although Im not usually a big fan of this phone, to make it appear like the old PBX style phones, this is perfect for that.
This is what this customer likes to see, if someone is on the phone or not.  Its a shared line to configure for these phones.