A coin door generally refers to the mechanism where users insert coins to play an an arcade machine.
A coin door can be added to your arcade cabinet purely as a decoration, or for functionality.
It is possible to wire up a coin door with switches and interface them to a keyboard encoder. The encoder sends a signal that corresponds to the "credit" command. This allows a coin to act as it would in a real machine. Most coin doors have the same type of switch as a normal arcade button which makes it simple to wire it up to your encoder.
You can also wire up the lights on your coin door by taking 5V or 12V power from your PC and running it to the light bulbs on the door. Additionally, many people modify coin doors to use LEDs instead of incandescent bulbs. The reason for this is the available colors and longevity. LEDs will last a hundred times longer than incandescent bulbs. Many people utilize 5V or 12V LEDs with resistors and connect the LEDs bulbs to the PC Molex Connector. Ensure the voltage on the positive side of the Molex connector matches the voltage of your LED or incandescent bulb.
Often called "Coin Mechs" or "Coin Acceptors", a coin mechanism is a mechanical or electrical device that discriminates between different types of coins and routes them to the accept chute, or the reject chute, as appropriate. Mechanical coin mechanisms use carefully machined parts to check diameter, thickness, and weight of the coin. A strong magnet also provides some protection against use of "slugs". A rejected coin is usually trapped at some point during the checking, requiring the user to press the "reject button" in order to allow the coin to drop out the reject chute.