AT&T MERLIN LEGEND Key System Planning page 136

Modifications
Step 6
5-6
Adding to the System
If rearranging modules in the control unit, the numbering plan will revert to the
factory-set two-digit plan. You must then reprogram the system:
1. Collect a clean set of Key System Planning Forms from Appendix A.
2. Locate the AT&T Equipment List, the local telephone company line
information list, the Floor Plan, and the analysis of the Employee
Communications Survey forms. If any of these materials has been revised,
you should have both the original and revised versions available.
3. Work through this book, starting at Chapter 2.