Relay board module is used for controlling higher current loads from your microcontroller development board, PC parallel port or Arduino Uno. This board has two on-board relay which can switch up to 7Amps. Relays terminals (C, NC, NO) are accessible through screw terminals which makes wiring up the board very easy. The relay is safely driven by transistor BC547 hence your input device, such as Arduino, is protected from relay circuit. There is free wheeling diode which will further protect your Microcontroller from relay kick back.