1. List the four main components of a programmable logic controller? processor unit, power supply, input/output device section [interface], programming device 2. Define the term Interface? An interface occurs when two systems come together and interact, or communicate. In the PLC it is between the inputs and outputs and the processor. This happens when any input or output voltage or current is changed to or from a low voltage signal that the processor uses internally for decision making. 3. Define the term real world? The term real world is used to distinguish actual devices that exist and must be physically wired from the internal functions of the PLC system that duplicate the functions of relays, timers, counters, and so on, even though none physically exist. 4. Define the term discrete? Discrete devices are either ON or OFF, OPEN or CLOSED. 5. Explain the following acronyms: DC Direct Current ADC Analog to Digital Converter AC Alternating Current CPU Central Processing Unit DAC Digital to Analog Converter PC Personal Computer PLC Programmable Logic Controller NEMA National Electrical Manufacturers Association I/O Input / Output 6. Define the term analog? An analog device has a range of possible values like pressure values, temperatures, variable speed drives. 7. List two types or styles of programming devices? They can be a hand held device or a PC. 8. True / False RELAY LADDER LOGIC is a high-level graphic computer language. 9. What is the major advantage of a PLC system over traditional hardwired control systems? Lower cost, less parts, reliability, programming fast and easy [tech friendly]