Multiplexer Module is a micro chip that requires 1 Analog Pin and 2 to 4 Digital Pins to allow the micro controller to monitor more Analog Pins for sensor readings. The requirement of 1 Analog Pin is actually the output pin shared among all the extension Analog Pins. The module only allow 1 Analog channel or sensor value to be connected to the output Analog Pin each at a time thus they take turns to operate.