The invention provides a solution/device for controlling external parameters by use of the same data cable and specific software to transfer/receive messages and monitor/control external parameters in a system. Additionally, the invention is compatible with ATA/ATAPI by using the ATA protocol or side-band protocol to make a main system communicate with other device(s) through an ATA/ATAPI device's data cable. Also, the invention uses the system's data cables and a non-standard controlling sequence to transfer and receive messages by the same cable to connect with the external devices for monitoring/controlling external parameters. Hence, the number of data wires needed is reduced. Also, the invention can decrease the manufacture costs and get a better heating dissipation.