AT&T Merlin Legend MLX-10 User Manual page 24

Your MLX-10 Telephone
ICOM Originate Only. Use this button to make inside calls;
calls do not come in on this button. This button is set up by
your company to make either inside ringing or voice-
announced calls.
555-1234. Use any button labeled with a phone number to
make or receive outside calls only. It is a direct outside line
that does not need a dial-out code.
Line Buttons
1-11