To provide a mobile data communication apparatus capable of communicating a data signal without wearing constraints of the mobile data communication apparatus.
The two-way communication system of this invention is provided with the mobile data communication apparatus 14 for communicating a data signal and a vehicle side data communication apparatus 15. The mobile data communication apparatus 14 is provided with two electrodes 17, 18 in contact with a body 12. The mobile data communication apparatus 14 detects the direction of a very small current of the data signal flowing between both the electrodes 17, 18. Then the mobile data communication apparatus 14 selects the electric coupling of the one electrode 17 to a communication circuit 20 and selects the electric coupling of the other electrode 18 to a ground circuit 21 on the basis of the detection result.
YOSHINO MASAKI
NAGAE TOSHIHIRO
