The Output Plug is a small board containing an 8-bit I/O expander plus NPN darlington array. Each pin can sink up to 500 mA @ 50V. Clamping diodes are included, so that relays and small inductive loads may also be connected.
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 ULN2803 and MCP23008 chips, as well as the 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 Output 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.