I will introduce you the port of the NXT at last. Here is the input port 1 through 4. Connect the sensor kind here. It seems like input port 4 is able to connect the "something" corresponds to the specification RS485, but such products has not been released yet.

The output is the opposite side. Port is a USB port and A to C, to the output port connects the motor and lights.

Here is a connector port is being used in the NXT (The photograph is a non-genuine are manufactured in Mindsensors.com). The part even point (nail) is shifted to the next, and shape is the same modular as phone jack. For details on how the allocation of some six terminal, please refer to the HDK.

Here is the connector of the USB. The shape of "A plug", is called "A receptacle". The terminals are only four. Because sending data one bit at a time in order (called serial communication), we can reduce the number of wiring. In addition, NXT is compatible with the communication speed of up to (12Mbps) Full-Speed.