RCA 26925 - Manual (Page 6)

6
Each Line on a Separate Modular
Jack
If you have two separate phone
jacks, each with its own line,
connect one of the phone cords
to the L2 jack, and connect the
remaining phone cord to the L1
OR L2 phone jack located on the
back of the phone.
NOTE: Connect the phone cord
from the L1 OR L2 jack to the
outlet that you want to be line 1.
NOTE: Two-line capability
requires two-line service from
your local telephone company.
Line 2 Line 1