Sangean ATS-909X w (R1) - Manual (Page 13)

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CHANGING BATTERIES
Press and remove battery cover in the direction indicated by the
arrow on the cover. Insert 4xUM-3 (AA Size) batteries with polarities
exactly as shown on diagram inside the battery compartment. Slide
battery cover back into place in direction of arrow until case snaps
into place.
Each time the ATS-909X is turned on the battery level indicator will
remain. Batteries should be replaced when battery level drops or
the level indicator flashes.
Batteries must be replaced within 3 minutes to retain clock display.
(Input memory will remain intact even during power failure because
receiver is equipped with EEPROM memory)
Note:
If you use non-rechargeable batteries, before inserting the batteries
make sure the Alkaline (Batteries) or NIMH/NICAD (Charger) switch
(which is located inside the battery compartment) is switched to
the Alkaline (Batteries) position. If you use rechargeable batteries,
make sure to switch NIMH/NICAD/Alkaline switch to the NIMH/
NICAD (Charger) position.
Note:
You may make sure to have the same capacity of the rechargeable
batteries, and then they can be balanced to full charge.