1.This is a very practical 16channel analog/demultiplex/demultiplex wide card CD74HC4067. This chip acts as a rotary switch internally routes a common pin (Com in the diagram on the card) to one of the 16 channel pins (Chanxx). 2.It can process digital and analog signals (the voltage cannot be as VCC), and it can be connected in direction. To control, connect the 4 digital outputs to the chip address selection pins (S0S3) and send it the binary address of the desired channel (see datasheet for details). This way you can connect up to 16 sensors to your system using only 5 pins! 3.If you want bidirectional communication, you can add a second card to route the Tx line from the microcontroller to the Rx line of the 16 devices. With multiple cards, you can create similar arrangements for I2C, SPI, etc. 4.Since Mux/Demux can also process digital signals, you can use it to transmit serial TTLlevel data to multiple devices. For example, you can use it to connect the Tx pins of 16 devices to an Rx pin on a microcontroller. Then you can select one of the 16 devices you want to listen to.