1. Data backup using an optional battery
　Built-in RAM data and clock data of a programmable controller are held by using an optional battery.
　The life of an optional battery is approximately 5 years (ambient temperature: 25ºC ). 
  For battery replacement guidelines, refer to the User's Manual (Hardware Edition) for the series used.
　When an optional battery voltage becomes low, the built-in RAM data and clock data held will be lost.

2. Data backup using an optional memory cassette
　Sequence programs are held in the built-in EEPROM of an optional memory cassette.
　Maintenance of the built-in EEPROM is not required. However, the number of overwrites is limited. For details, refer to the User's Manual (Hardware Edition) for the programmable controller used.

3. Data backup using the built-in EEPROM of a programmable controller
　Latched device data and sequence programs are held in the built-in EEPROM of a programmable controller.
　Maintenance of the built-in EEPROM is not required. However, the number of overwrites is limited. For details, refer to the User's Manual (Hardware Edition) for the programmable controller used.