US Patent 7447552 Common transmission protocol system for an automation device

An automation device is disclosed, in which a multiplicity of physically distributed functional units communicate with each other by means of a common transmission protocol. The device has a microcontroller (110), which has a group of associated input/output connections which are connected to a resistor network. The resistances of the resistors follow a sequence, the resistance respectively being doubled from the less significant to the next most significant bit. Each input/output connection is actively switched to the associated logic level in order to output a first logic state and is connected as a high-impedance input in order to output the inverse, second logic state.