The Relay Shield utilizes four high quality relays and provides NO/NC interfaces that control the load of high current. Which means it could be a nice solution for controlling devices that couldn¡¯t be directly controlled by Arduino¡¯s Digital I/Os. Standardized shield form factor enables smoothly connection with the Arduino. The shield also has four dynamic indicators show the on/off state of each relay.Features:Arduino/Seeeduino compatibleStandardized shape designWorking status indicators for each relayHigh quality relaysProvides NO/NC interfacesSpecification:CHANNEL1 Interface:COM1- Common pinNC1- Normally Closed. Will be connected with COM1 when RELAY1 pin is set low and disconnected when RELAY1 is high;?NO1- Normally Open. Will be connected with COM1 when RELAY 1 pin is set high and disconnected when RELAY1 is low;4 Digital Pins to control 4 Relays: RELAY1-RELAY4 pins could be connected directly with Arduino pin number of 7-4, so that four relays could be easily controlled by the ArduinoDocuments:Please visit our wiki page for more info about this product. It will be appreciated if you can help us improve the documents, add more demo code or tutorials. For technical support, please post your questions to our forum.