 In contrast to protocols (such as Ethernet) that use random back-off delays before issuing a retry, I2C has a deterministic arbitration policy.Each transmitter checks the level of the data line (SDA) and compares it with the levels it expects; if they do not match, that transmitter has lost arbitration and drops out of this protocol interaction.If one transmitter sets SDA to 1 (not driving a signal) and a second transmitter sets it to 0 (pull to ground), the result is that the line is low.