Sun Telecom ST800 User Manual page 10

A maximum of 14 messages can be locked.
Select a message to be locked and press the Function
button.
When "LOCK?" is displayed, press the Read button to lock
the message. The Lock icon will be displayed, and the
message will be locked.
To unlock messages, select the message to be unlocked
and then press the Function button to display "UNLOCK?"
on the screen.
Press the Read button.
Locked messages will remain in memory even during low
battery power, and while the battery is being changed.
Press the Lamp button twice to escape to the standby
screen.