The onboard Atmel 328 based microcontroller transmits wheelchair direction commands as characters to a modified Eightfold Technologies SmartChair Remote [22] via serial communication. The system outputs characters based on the thresholding algorithm output: front (f), back (b), right (r), left (l), stop (s). The SmartChair Remote emulates a joystick and was connected in parallel to the wheelchair mechanical joystick, producing similar voltages as the joystick. SmartChair Remote modifications included a read data function from the ultrasonic tethering system.