3 555 timers used to control a DC brushless 3 phase motor like a HDD motor. The LED's represent the 3 coils. When the LED is off that 555 is sinking or grounding that coil because the common wire is always positive. The potentiometer hooked up to pin 5 of all the timers is a way to fine tune how fast the motor turns or in this case the LED's flash.
