other interface units contain thermocouple amplifiers or bridges for use with resistive sensors. A data transmitter unit will have the capability of controlling 8 actuators and will contain 8 digital-to-analog convertor(DAC)to change the digital data to an analog format for each actuator being controlled. this set up is shown in fig. 13.10. each input or output requires its own interconnect cable or bus resulting in a mass of wiring which requires careful routing and identification marking.