Casio Casiotone CT-S1 User Manual page 10

Battery Replacement Required
Indicated when the TONE VARIATION LEDs flash.
• Low battery power may cause notes to become distorted, or other problems.
• You can conserve battery power by using headphones and by reducing the volume level.
• Continued use with low batteries may cause power to turn off suddenly. This can cause
stored data to be corrupted or lost.
EN-9
Getting Ready to Play