I have a potential customer with a Toshiba DK-14 telephone system. They have 10-button 2-line LCD digital speakerphone sets. Now my company generally deals with Partner, Legend, and IP Office systems. It's been a while now that I have installed their system for them as a favor but are looking to add them as a customer. My question is, how do I change the line ringing on this system? Any information would be helpful, because I am totally green to the programming of this system. Thanks!