The CR-400 readout unit, when connected to your mass flow control-ler or meter with a cable, provides the key mass flow functions, such as flow measurement and control as well as cumulative flow calcula-tions and flow event outputs. This readout unit offers RS-485 commu-nications capability, so multiple readout units can be controlled online by a host computer. * The CR-400 is fully compatible in size with the CR-300.