HP Jornada 420 - Manual (Page 17)

Chapter 2 | Setting up | 13
The rechargeable backup battery is a permanent part of the
HP Jornada, so you do not need to install or replace it.
The backup battery is charged automatically when the P/PC is
connected to AC power.
Make sure you connect to AC power to charge as soon as you
see a backup battery low warning.
Do NOT replace your main battery when the backup battery is
low.
Using the cradle
The views below show the features of the cradle and how the
P/PC docks with it.
1. Release buttons—To release the HP Jornada from the cradle,
press the buttons on both sides of the cradle.
2. Connector to the P/PC—Connects the cradle to the P/PC.