The SDM-SIO4 is a legacy product and should be purchased only as a replacement or for use with legacy data loggers such as the CR10X. When considering the purchase of an SDM-SIO4, first consider using the SDM-SIO1 instead. Please note that the SDM-SIO4 is not compatible with all data loggers. Primarily for legacy data loggers, the SDM-SIO4 adds serial I/O capacity and flexibility. It has four serial ports that communicate with serial sensors, display boards, printers, and other serial devices. After being programmed, the SDM-SIO4 communicates with connected devices in parallel with the data logger's own program sequence.