Certainly is. I tried to find the post where I wrote out the procedure but can't find it. Grrr.
Ok, gotta be careful cos if you stuff it, you'll have to reprogram the system from scratch.
You'll need the programming tool or knowledge of how to program via the handset.
Switch the memory switch on the main equipment to clear, and then either connect to the system or go into programming mode over the handset using password ******* (7 stars). Quickly before power goes out or anything, change the password to something that you'll remember.
Change the switch back to normal so programming isn't defaulted when the system loses power.
After that you're all done