Patent ID: 7158561

Claim:
A communication system comprising: a plurality of communication devices being connected to a transmission line and divided into one master communication device and other slave communication devices to logically form a star-type connection and adjusting transmission timing of data based on a detection result of a carrier signal of another communication device to prevent a collision between signals, thereby performing transmission or reception of the data via the master communication device, wherein the data includes first multi-address data to be relayed, ACK data representing a reception confirmation of the first multi-address data, second multi-address data for relaying the first multi-address data, third multi-address data for relaying the first multi-address data, and general data, the master communication device includes a transmission control unit configured to transmit the general data at a random time determined by random numbers set after elapse of a first time and before elapse of a second time from a time when the carrier signal on the transmission line is gone, when newly transmitting the data, and to transmit the ACK data to the transmission line before elapse of the first time from a time when the master communication device confirms reception of the first multi-address data and, when the first multi-address data is received, to transmit the second multi-address data to the transmission line before elapse of the first time from a time when a carrier signal of the ACK data is gone, and to subsequently transmit the third multi-address data before elapse of the first time from a time when a carrier signal of the second multi-address data is gone.