I have been trying to replicate 'key system' functionality for a new system install. I think I've gotten the Asterisk side of the configuration figured out but I'm having trouble with the phones. I can get the phones to register but each line I register requires two buttons on the phone, one for the extension, and one for the 'line key'. I can't figure out what I'm doing wrong here on the phone configuration. If anyone has successfully gotten SLA working with Asterisk 1.6x and the SPA50X phones, your assistance would be greatly appreciated.