Transmitter and Receiver: These provides the link between the robot and the human operator. Commands are entered through the joysticks and buttons on the RF Transmitter, and sent through the air via FM radio waves to the RF Receiver module mounted on the robot. In addition to providing the control link, the transmitter can be used to alter robot control options, such as drive configuration and joystick trims and scaling.
Tether Port: Sometimes for diagnostic purposes, it may be useful to plug the transmitter directly into the Microcontroller, and bypass the need for the RF Receiver. This would help you determine, for instance, whether radio interference is at fault for your robot behaving strangely, or if some other factor is to blame. In order to use the tether feature, you will need to purchase a cable. Any telephone handset extension cable will work (the coiled cable that goes from the handset to the base of a corded phone, not the cable that goes from the phone to the wall).