Once you unfold the keyboard, you have to slide the two sides inwards so you can then use it. It has a built-in dock that you connect and rest your iPAQ on to so you can type using this full-size keyboard on a very tiny screen!
The battery doesn't work in this iPAQ so I can't try this great little keyboard out and I can't seem to find a replacement battery on eBay right now but I've only been searching using the iPAQ model number so what I need to do now is either find a service manual and get the part number or (the more interesting way) take it apart to see if there is a part number on the battery itself...
I've just gotten around to finding out the part number of the battery and you'll never guess which method I chose!
There are 4 tiny torx screws holding the back on the Compaq 3660 iPAQ and then all you need to do is take an appropriate spudger and carefully prise the back off.
Now I have a part number I'm off to do some hunting, unfortunately most of the new compatible batteries for these old iPAQ's used to come from China via eBay but with all that's currently going on with the Corona 19 Virus I'm not sure if anyone will be posting any from there at the momen.