The Auto Answer Switch is located on the back of the charging base to the right of the phone cord connection.

CS510/520/540
RED = Auto Answer Off
(Press headset button to turn headset on / answer a call)
GREEN = AUTO ANSWER ON
(Lifting headset from the base will automatically turn it on)
CS530
Grey = AUTO ANSWER ON
(Lifting headset from the base will automatically turn it on)
Black = AUTO ANSWER OFF
(Press headset button to turn headset on / answer a call)
Note: After turning this feature on, you may need to reconnect the power cord to the base for Auto Answer to work.