JP2724363B

PURPOSE:To send a data between 1st and 2nd units without any error by utilizing electromagnetic coupling so as to demodulate the data based on a pulse width. CONSTITUTION:A data communication equipment has a write/readout control unit 1 being the 1st unit and an ID unit 3 being the 2nd unit fitted to a commodity 2 or the like. The unit 1 has 1st and 2nd coils L1, L2, a unit 3 has a 3rd coil L3 and a serial data is sent as semi-duplex data between the 1st and 2nd units by utilizing the electromagnetic coupling. After a host controller 4 sends a transmission control signal CT to the write/readout control unit 1, the transmission data SD is sent and the reception data RD is read. Then the data demodulation means of the 2nd unit demodulates a signal based on the pulse width, then a comparatively simple circuit is attained and power consumption is less.