The Touch Sensor Module utilizes a floating lead on a Darlington transistor to detect a touch. There are 2 LEDs on-board.  A red LED lights when power is applied.  A green or red LED lights when a touch is detected. Features: Main chip: LM393 Working voltage: for DC 5V Single-channel signal output Low-level output signal used for human body touch sensor alarm Adjustable sensitivity Pin Connector to board: 4 Pins Package Includes: 1 x Touch Sensor Module Category: Electronic Switches/Keypad