COMMUNICATION TERMINAL DEVICE

摘要

PROBLEM TO BE SOLVED: To provide a portable telephone set which can be easy to hold, and easy to operate basically in one hand with the thumb motion of key operation. SOLUTION: The surface of a key operation part in which the ten keys of a portable telephone set or the like are arrayed is shaped like a recessed curved surface, and the surfaces projected from the recessed surface of the keys are allowed to almost follow a virtual curved surface in parallel with the recessed curved surface. Thus, when the portable telephone is grasped between the palm of a user's hand and his or her thumb, the thickness of the part having the key operation part of the portable telephone set caught between the surface of the palm of the user's hand and his or her thumb is made almost equal.