When I pick up the receiver (22 button non-display) and touch an outgoing line button, the receiver rings busy. When I put a 22 button display phon on that extension (205) and try to get an outside line - the display states "Restricted" and rings busy.

I am also confused as to the jargon with this system
COS - ?
FF- I assume they are the function keys on the top of the handset (and in order)

Thanks - Mark