PURPOSE: To reduce the cost and to improve the workability by providing a structure for jamper shortcircuiting a backup power source.

CONSTITUTION: A circuit 1 is operated through a main power source 2, and when the main circuit 2 is removed from the circuit 1 in order to replace the main power source 2 the circuit 1 is backed up by a backup power source 3 thus holding the content of the memory in the circuit, i.e., program data and the like. The backup power source 3 is mounted on a circuitboard and connected with the circuit 1, when the main power source 2 is connected with the circuit 1 which is in standby state, by shortcircuiting a jamper 4. Since the backup power source 3 can be connected with the circuit 1 through simple soldering work of the jamper 4, the workability can be improved with low cost.