Programmable automation controller (PAC) systems consist of PAC modules, each of which performs a specific function. PAC systems are used in motion control, machine control, machine vision, and other industrial control applications. They include the following types of PAC modules: analog I/O modules, digital I/O modules, relay modules, counter modules, serial modules, servo or stepper controller modules, timer modules, and data acquisition modules. PAC systems with analog I/O modules are used to measure and control industrial automation devices such sensors and actuators. They can also be used to condition high or low voltage signals, thermocouples, resistance temperature detectors (RTD) and strain gauges. PAC systems with digital I/O modules are used to measure and control industrial automation devices such sensors and actuators. PAC systems with data acquisition modules digitize and process multiple sensor or signal inputs for monitoring, analyzing and/or controlling systems and processes. PAC systems with serial modules coordinate the flow of data, control signals, and timing information between data terminal equipment (DTE) and data communication equipment (DCE).