Patent ID: 7123888

Claim:
A variable communication system characterized by comprising: a transmission device including information amount magnitude discrimination means for discriminating whether an amount of information to be transmitted per unit time is greater than or less than a threshold amount, first communication data sending means for, when said information amount magnitude discrimination means discriminates that the amount of information to be transmitted is a first amount, digitally modulating first information as the information into information in a signal form having a predetermined bandwidth with a predetermined center frequency, and sending out the information as communication data, and second communication data sending means for, when said information amount magnitude discrimination means discriminates that the amount of information to be transmitted is a second amount, digitally modulating second information as the information upon performing spread spectrum to obtain the same bandwidth as the predetermined bandwidth with the center frequency, and sending out the information as the communication data, and a reception device including demodulation means for demodulating the communication data sent from said transmission device, de-spreading appropriateness discrimination means for checking whether or not a signal after demodulation can be normally de-spread, first information reproduction means for, when said de-spreading appropriateness discrimination means discriminates that de-spreading cannot be normally performed, reproducing the first information from the signal after demodulation by said demodulation means, de-spreading means for, when said de-spreading appropriateness discrimination means discriminates that de-spreading can be normally performed, de-spreading the signal after demodulation by said demodulation means, and second information reproduction means for reproducing the second information from the signal after de-spreading said de-spreading means, and wherein the first amount is greater than the threshold amount and the second amount is less than a threshold amount.