Raspberry Pi PWM HAT with modification 16-channel PWM/Servo HAT with modification (top left) to connect GPIO pins to the four 3-LED signals in the "Parking Lot". Across the top are the 16 sets of 3-pins, each set to control a servo, which will change the aspect of a semaphore signal. In front are the 40 pins interconnecting the Pi underneath and the bonnets on top. Power plugs to drive the servos are on the right.