These Thermo Scientific interface cables are used to connect the Thermo Haake ARCTIC AC200 series temperature controller via USB port to a desktop or laptop computer. The NC serial communications protocol is based on a master-slave model. The master is a host computer, while the slave is the chiller's controller. Only the master can initiate a communications transaction (half-duplex). The slave ends the transaction by responding to the master’s query. The unit can be controlled through your computer’s serial port, a standard connection now days.