A relay is an electromagnetic switch. Applying current causes the electromagnet to become active and pull the contacts together. On the schematic, the electromagnet is the part of the symbol that looks like half a transformer or inductor. The contacts are right beside (or above or below) the coil. These contacts can take on any of the normal switch configurations. Pictured here is a simple SPST (or Single Pole Single Throw) relay. This means the the Relay contains one set of contacts and can only be switched one way (on or off). Other types of relays include SPDT (Single Pole Double Throw-A relay with one contact that can be toggled both ways), DPST (Double Pole Single Throw-A relay with two contacts that can only be on or off) and DPDT (Double Pole Double Throw-A relay with two contacts that can be toggled both ways).