AT&T ML17959 - Manual (Page 17)

Getting started
12
Installation options
Hold down the switch hook on the telephone base, then slide the handset
tab upwards to remove it from the slot. Rotate the handset tab 180 degrees.
Push the handset tab down into the slot until it locks into position. 2.
Follow the steps in Telephone base installation on pages 5-7 to install
your telephone for tabletop use.
3.
Switch hook