the control unit 3 specifies the number according to a position of the contact the contact range of the contact is compared with a threshold value to thereby determine whether the input is a finger tip input or a finger pad input s 3002 the control unit 3 stores the numeral input and the input method used s 3003 when the number of the input and the password registered earlier matches s 3004 yes and the input methods thereof matches as well s 3005 yes the control unit 3 increments the counter s 3006 when the counter is not greater than 4 s 3007 no the control unit 3 proceeds to the step for inputting the next password number when the counter is greater than 4 s 3007 yes the password is authenticated s 3008 and the lock is canceled meanwhile in cases where the number of input and a password do not match s 3004 no or in cases where the number of input and a password match but their input methods do not match s 3005 no the control unit 3 displays a message to inform the password or the input method is wrong s 3009 the password cancellation thus terminates it is to be noted that a plurality of input methods may be registered for one password for example in the case shown in fig1 b three types of input methods are registered for.