thanks to everyone for the replies. the system involved is a Definity G3 SI release 11 or 12. I have looked through the man pages (gasp!) and it seems that I need to do this:

1) locate the TN763 pack
2) wire from the pack to the Magic (RCA - how do you do that ?)
3) complete CPE Trunk Group form
4) complete Feature-Related System Parameters form

I haven't found specific details on completing those forms. Can anybody point me to a step-by-step ?