The present invention relates to a transmitting/receiving device for easily inputting a unique identification ID for communications by using one or two digit input units, which refers to a hand-operated switch, a sensing unit of a touch pad or a touch screen, in such a manner that each digit of ID in a decimal/hexadecimal positional notation is inputted to an input port of a microcontroller by repeating toggle operation of the digit input unit n times to input a digit value n as decimal/hexadecimal value, and position of the digit to be inputted is changed by means of that for a predetermined time the digit input unit is operated or not operated, and a microcontroller or the like calculates an communication device ID by means of the combination of inputted digits and position changes according to principles of the positional notation.