An exemplary stair nosing assembly comprises an elongated base, a plate adhered to the base, and a cover temporarily covering the base and the plate. The PWM signal generating circuit generates a PWM control signal with a sequence of alternating on-time and off-time, and the driving circuit outputs a driving signal according to the PWM control signal to a fan motor. Upon selection of an offer, the system may determine which offer the recipient selected by determining which frame was displayed when the recipient responded.