Relays are the switches that aim at closing and opening the circuits electronically as well as electromechanically . It controls the opening and closing of the circuit contacts of an electronic circuit. When the relay contact is open (NO), the relay isn't energized with the open contact. https://youtu.be/ak13PMyCfJg Item number: 2968016 Packing unit: 1 pc Minimum order quantity: 1 pc Sales Key: C31 Product Key: CK621A GTIN: 4017918130732 Weight per Piece (including packing) : 39.82 g Weight per Piece (excluding packing): 31.06 g Package Includes: 1 x PHOENIX Contact Relay With Base 24V DC