Sony TA-A1ES Operating Instructions Manual page 15

Inserting batteries into the remote control
Insert two R03 (size AAA) batteries in the remote control.
Observe the correct polarity when installing batteries.
Notes
 Do not leave the remote control in an extremely hot or humid place.

Do not use a new battery with old ones.
 Do not mix manganese batteries and other kinds of batteries.

Do not expose the remote sensor to direct sunlight or lighting
apparatuses. Doing so may cause a malfunction.

If you do not intend to use the remote control for an extended period of
time, remove the batteries to avoid possible damage from battery
leakage and corrosion.
Tip
When the remote control no longer operates the amplifier, replace all the
batteries with new ones.
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