This module contains 4 relays, which is working at 5V while the Max current is 10A. There're led indicators on the board to show you the working status of the relays.
1. DC+: 5V input
2. DC-: Ground
3. IN1-4: INPUT of Relay 1-4
4. NO1-4: Normal open of relay 1-4
5. COM1-4: COM of relay 1-4
6. NC1-4: Normal connected of relay 1-4