• A relay in an electronic circuit is:

A device which switches the mains supply on or off using a low voltage/current output

• It consists of an electromagnetic switch operated by a small current in the coil to convert a small electrical input to a higher current output
• A relay can act as either a switch or an amplifier for the electric circuit

• A single relay can activate multiple circuits, allowing one input to initiate many other outputs
• They are also commonly used in combination to perform Boolean logic functions such as AND or NOT gates
• Relay’s come in two types:
  • Normally open (NO)
  • Normally closed (NC)
• Most relays are type NO
• When the relay is activated, the contacts connect the circuit (like closing a switch) and the circuit is disconnected when the relay is inactive
• NC relays disconnect the circuit when the relay is activated, and the circuit is connected when the relay is inactive