PURPOSE: To cope with change in a code system only with table replacement by transiting a state, referring to a state transition table with tree structure, and obtaining meaning of undifined length code according to the transition state.

CONSTITUTION: In a code decision means 30, a code length counting part 30a counts time length of code components and clearance between code components. According to results which are calculated by the counting part 30a, a code decision part 30b decides whether inputted code components are dashes or dots, and clearance between code components is included in the same code or means termination of one code. For a meaning interpretation means 31, the meaning interpretation part 31a detects termination of undifined codes by the means 30, obtains their meaning according to a state transition table 31b and outputs the meaning on a display part 32.