monitor rclk 208 through the amplifier 222 the rack line 224 is similarly configured as rclk 208 except that the slave 226 is able to pull rack 224 low and the master 228 is not able to do so the rdat line 230 is similarly configured as rclk 208 and rack 224 except that both the master 232 and slave 234 are able to pull rdat 230 low the embodiment of the present invention allows several devices to communicate with each other data transfer may occur in any direction that is from the master to the slave or from the slave to the master fig3 illustrates the basic communication sequence 300 for any device to communicate all devices begin in an idle state 302 the device initiates the sending of data 304 transmits an address 306 transmits data 308 transmits a stop signal 310 and returns to the idle state 302 the idle state 302 exists when at least a master and a slave are connected on the bus in the neutral or disconnected state all three lines rclk rack and rdat are high when a slave is attached the neutral state is to pull the rack line low indicating the presence of at least one slave device as several slave devices are attached to the bus each one will pull the rack line low when it is turned on and functioning the device initiates sending of data 304 by sending a start command the start command is to bring the rdat line low while in the idle condition this signals to all devices that a transmission is about to begin the device sends an address 306 if the communication is originating at the master.