Feature: This module can be connected to digital I/O port, when the input of S port is low level, relay will be under ‘disconnect' state. Relay will be under ‘connect' state when the input of S port is high level. It can be connected in series to the LED lights, buzzer or even the loop of a small lamp so as to control the state of the switch. Brick Interface: 3PIN 4PIN Brick Power: Supply 5V Board Size: 36 × 24 × 1.6mm Package Included: 1 x 5V One Channel Relay Module Compatible to AC 120V DC 24V 2A 3P/4P Interface