Jake:
For a Merlin Legend you need to first map the phone for a Merlin system - the default mapping I think is for a Partner system (the re-mapping procedure is in the "Installation and Use" manual. Next, you need for the merlin system to have an ATL card (408 or 008). You cannot use an MLX card. The radio module should connect to any port on an ATL card. In extensions programming on the Merlin system, indicate the ATL port as a BIS-22. You can program either up 8 or 12 buttons on the phone. The default is it reserves several buttons on the second row for available lines and the bottom row of buttons is for intercom and "drop" "conference". That's about it...it's pretty straightforward...Make sure the radio module is placed somewhere mid-ceiling level and a good distance away from the control unit. You should easily get 800 to 900 feet of range if the radio module is placed correctly...Tom