PURPOSE: To restrict a working channel only to one wave by transmitting/ receiving data to/from a master station when an IC card to be a slave station is included in a service area of a master station is decided from a level found out by receiving radio waves from the master station.
CONSTITUTION: Radio waves radiated from an antenna of the master station 1 are received by an antenna 4 of the IC card 3 to be the slave station. A control circuit 11 switches a transmission/reception switching circuit 6 to a receiving circuit 8, and when a noise component is detected by a noise component detecting circuit 9, a noise pulse counting circuit 10 counts up the noise pulse. When the count value is less than a prescribed value, that the IC card 3 is included in the service area 5 is decided and data are transmitted by a transmitting circuit 7.
SATO KOICHI
HARAKAWA KAORU
| JPS62266688A | 1987-11-19 | |||
| JPS54154295A | 1979-12-05 | |||
| JP63199363B |