Patent ID: 7925215

Claim:
A communication system comprising: an initiator as a communication device that starts communication by outputting an electromagnetic wave, and transmits a command via the electromagnetic wave; and a target as a communication device that transmits a response to the command by load-modulating the electromagnetic wave, wherein the initiator has means for causing a command where a first value is set in time slot information to be transmitted when, of passive mode communication and simple mode communication, the passive mode communication is performed, the passive mode communication including transmitting the command including the time slot information related to a time slot, and receiving a response to the command, the response being transmitted by the target at a timing of any one of one or more time slots and including an ID (Identification) for identifying the target, to acquire the ID for identifying the target, and identify the target by the ID, the simple mode communication including transmitting the command, and receiving a response to the command, the response being transmitted by the target at a timing of any one of one or more time slots and including real data, to acquire the real data, and means for causing the command where a second value different from the first value is set in the time slot information to be transmitted when the simple mode communication is performed, and the target has means for recognizing the time slot information included in the command from the initiator, means for determining a time slot for transmitting the response by a random number, and causing the response including the ID for identifying the target to be transmitted at a timing of the time slot determined by the random number, when the time slot information has the first value, and means for causing the response including the real data to be transmitted at a timing of a preset time slot, when the time slot information has the second value.