The Analog Plug is a small board containing the MCP3424 analog-to-digital converter with I2C bus interface. The ADC can take 4…240 samples per second, depending on resolution (12..18 bits). It has 4 differential input channels and supports a differential voltage range from -2.048V to +2.048V, full scale. Tie the "negative" side to ground for single-ended use and restrict the "positive" input to positive volts with respect to ground.
An I2C bus running at 3.3V is used as interconnect, with all the power and signal lines brought out to to both sides of the board to allow daisy-chaining with other I2C-conformant boards.
The pre-assembled version comes with the SMD-sized MCP3424 chip and decoupling capacitor already soldered onto the board. Note that no 6-pin headers are included.
The PCB only variant contains just the board for the Analog Plug. No parts, no headers.
As connectors you can use a Plug Headers set with 10 male and 10 female 6-pin headers, which makes it easy to connect multiple plugs and JeeNodes in a "standard" way. Or you can solder the board directly in place for more permanent use.
The documentation and full design details are freely available.