AASTRA DT292 for MD Evolution User Guide EN - Manual (Page 127)

127 MD Evolution – Cordless DT292
Installation
Changing the battery
Rechargeable batteries have a limited life span. If the standby time
for the phone becomes too low, you should replace the battery.
Please contact your system administrator or supplier for more
information.
Note: Only use the specified batteries (NiMH pack 600
mAh, 3.6 V).
Do not disconnect or exchange the battery unless it must
be replaced. Do not charge the battery outside the phone.
The battery does not contain cadmium and is therefore more
environmentally-friendly than other rechargeable batteries.
However, all batteries should be treated as chemical waste.