Unlinking Keypad?

Anyone know how to unlink a keypad to the base station?

I've got an extra keypad which was linked to an failed basestation.  

I've got a new base station that came with a keypad.  How can I unlink a keypad from a base station so that I can add it to the other base station?  The base stations are the same 3rd gen version.

The extra keypad keeps saying "keypad out of range. press any key to tray and reconnect to the base station."  Whenever I push a button, it says "connecting to base station".  Can't get it to go to menu.

cheers