AT&T 9230 - Manual (Page 11)

10
TELEPHONE OPERATION
Headset Jack
You can use this telephone hands-free
when you install a 2.5 mm headset
(SKU 24099), purchased separately.
Plug the headset into the jack located
on the right side of the handset
(under the small rubber flap). Do not
force the connection, but make sure
the plug fits securely.