120-Volt Duplex Electrical Receptacles

• Standard 120-volt duplex electrical receptacles have two outlets, each with two parallel slots (one for the attached black live wire's terminal, one for the attached white neutral wire's terminal) and an arched slot at the bottom (for the attached ground wire's terminal). These receptacles come in 15 and 20 amp sizes, and though 15 amp receptacles are generally used for most appliances, 20 amp receptacles are installed when the appliances require 20 amps or less.
  
  

GFCI Receptacles

• A GFCI receptacle (Ground Fault Circuit Interrupter) has two outlets like the standard 120-volt receptacle, but the GFCI (also known as a GFI) has its own internal circuit breaker that switches off if there is a short or power surge in the circuit it is attached to, or if there is a problem with an appliance plugged into the receptacle. Each GFCI has a TEST and RESET button on its front between the two outlets for the GFCI to be turned back on if it automatically trips. GFCIs are required by code to be installed in areas with water usage, such as kitchens, bathrooms, outside areas and utility rooms.
  
  

240-Volt Electrical Receptacles

• 240-volt electrical receptacles have one outlet, with two live slots and a ground slot. They are used for appliances such as power tools that require 240 volts, and are available for mounting either recessed into the wall, or on the wall surface. Some 240-volt receptacles have a feature that locks the appliance's plug into the receptacle to stop it from accidentally pulling out.
  
  

120/240-Volt Electrical Receptacles

• 120/240-volt electrical receptacles provide both 120 and 240 volts. They have four slots: two live, one neutral and one ground. Like the 240-volt receptacle, these receptacles are available for recessed or surface mounted installation. The receptacles are generally black in color, with the ground slot at the top of its circular (or sometimes square) face, the neutral slot at the bottom, and the two line slots on each side.