control means for discontinuing energization of the drive motor in the event the speed of rotation of the beater brush drops below a preselected speed, said control means including a sensor, means for pulsing said sensor for generating sensor outputs responsive to the speed of rotation of the beater brush, first timing means for delaying operation of said control means for an initial power up time period starting from the initiation of energization of said drive motor, and second timing means for initiating a control function in the event the time period between sensor outputs exceeds a preselected time period, said first and said second timing means employing separate distinct components for their respective timing functions.