5) WHAT IS GND AND IS IT THE SAME AS EARTH GROUND?
Answer: GND stands for Signal Ground. It refers to the ground side of a power supply. This is different from Earth Ground, which is usually connected to the earth by a ground stake near the point where electrical power enters a building, and is distributed through the building wiring. Signal Ground creates a common ground reference for the connected devices on a cable, improving signal reliability. (More technically, Signal Ground improves performance of receiver circuitry where a common-mode voltage is present on both sides of differential signals, such as signals used by RS422 and RS485 differential transmit / receive lines, by providing a common ground voltage reference for the transmitters and the receivers.) DO NOT connect GND to Earth Ground, as this will degrade signal performance.