The S66 is designed to modulate the speed of a motor based on a 0 to 10 VDC input signal. The input signal can be supplied by any external source including those referenced to temperature, pressure, humidity, or flow. The S66 requires a 24 VAC power supply that is of the same phase as the AC voltage (motor) being varied. It features a hard start of motor and Built-in radio Frequency Interference Suppression.