This is a breakout board for the highly mobile 16-channel analog/digital multiplex / deultiplexer CD74HC4067.
This chip is like a rotating switch - it routes the common pin (COM in the schematic, SIG on the board) to one of the 16 channel pens (CHANxx). It works with both digital and analog signals (the voltage cannot exceed VCC) and the connection function in both directions. To operate it, connect 4 digital outputs to the chip address select pens (S0-S3) and send it the binary address of the channel you want (see the data sheet for details). Allows you to connect up to 16 sensors to your system using only 5 pins!As the mux/demux also works with digital signals, you can use it to piping TTL level serial data from or from multiple devices.To use the example, you can use it to connect the TX pins of 16 devices to an RX pin on your micro controller. You can then select one of those 16 devices to list. When you communicate two ways, you can add a second board to stir the TX line of your micro controllers to RX lines from 16 devices. By using multiple boards, you can create similar arrangements for I2C, SPI, etc.The internal switches are bi-directional, support voltage between ground and VCC, have low "on" resistance and low "off" leakage, and to prevent them from becoming frizzy, preform "breaking for making switching. The board also breaks out of the "public" pin, which when it drives high, the ordinary pin will fully disconnect (all switches "off").

Features
Use a channel of ADC to collect 16 channels analogue signal
Operating Voltage:2V to 6V
"On" resistance: 70 Ohms @ 4.5V
6ns break-for making @ 4.5V
Analogue signal input:C0-C15, 16 channels
Analogue signal output:DIG
Channel control:S0-S3