This is working for external calls transfered to my extension. But when an internal person calls my extension, they are getting a busy signal!? What do I need to do / change so that the second line rings for internal calls, and they dont get a busy signal?

I'm using a 424i, with this for the CF-NA:
#603
500 ( Our voice mail extension )
Speed Dial
12 ( time delay )
Redial
Speaker