Power Supplies - External/Internal (Off-Board)  Definitions

"Power Supplies - External/Internal (Off-Board)" largely refers to the devices that supply electric power to an electrical load. The primary role of these power supplies is to convert one form of electrical energy to another and, as the name suggests, they usually convert electric current from a source to the correct voltage, current, and frequency to power the load. 

1. Power Supplies: These are devices or systems that supply electrical or other types of energy to an output load or group of loads. They can receive energy from various types of sources, such as batteries, DC or AC input, solar energy, etc. and then convert it into the form required by the load(s). Power supplies often convert the energy into electric form.

2. External Power Supplies: These are standalone devices separate from the main unit. They plug into a wall socket and convert AC from the grid into DC power, and shift the voltage level to what the device requires. A common example would be the power brick used to charge a laptop.

3. Internal Power Supplies: These are typically found inside the casing of the equipment they power, often seen in computers, where the power supply is housed within the desktop or server chassis.

4. Off-Board Power Supplies: This term refers generally to power supplies that are not located on the main circuit board they are powering. External and internal power supplies could both be considered "off-board" if they are not located on the primary circuit board of the system. 

Each type of power supply is designed to meet the specific requirements of the device or devices it powers, considering factors such as location, energy efficiency, heat management, and the electrical demand of the device.