ELECTRONIC INSTRUMENT

PROBLEM TO BE SOLVED: To reliably backup and hold important data at the time of a power trouble such as an accidental power interruption, etc., by prolonging the life of a secondary battery to the utmost. SOLUTION: At the time of the accidental trouble of power, backup power is supplied to a memory 113 for storing data which has to be backed up by a battery 14. One circuit of the contact of a main switch 18 for supplying or disconnecting the main power of a device is used to be linked with a main switch 18 and when the main power is disconnected by the switch 18, the supply of the backup power to the memory 113 from the battery 14 is stopped to reduce the number of times of the charging/discharging cycle of the battery 14 to prevent the deterioration of the battery 14 to prolong the life of the battery 14.