Sony VGN-TZ340NCP - Manual (Page 25)

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Getting Started
4 Rotate the battery pack in the direction of the arrow and push in the battery pack until it clicks into place.
5 Slide the battery LOCK switch outward to secure the battery pack on the computer.
✍
When your computer is directly connected to AC power and has a battery pack installed, it uses power from the AC outlet.
!
This computer is designed to operate only with genuine Sony batteries.