Abstract: A caliper unit has a connector having connecting terminals. The caliper unit measures a value of a product, and generates digital data representing this value. A data-transmitting apparatus has a housing. The housing can be attached to caliper unit. The housing has a fastening ring and a connecting plug. The plug can be connected to the connector of the caliper unit by the fastening ring. A microcomputer including a CPU is provided within the housing. A RAM is also provided within the housing, for storing the digital data input from the caliper unit and also an identification (ID) number assigned to the data-transmitting apparatus. The microcomputer forms a serial-data message from the digital data and the ID number, both stored in the RAM. A transmitter is provided within the housing, for transmitting the serial-data message in the form of a radio message.