MK2 Twin Fan Controller/ Slave easy environment control The SMSCOM Twin Fan Controller 4.5amp Mk2 controller represents a real step forward in automatic temperature control. Unlike other controllers that simply shunt fans from idle to full speed after the temperature is exceeded, the Twin Controller automatically calculates the exact running speed for your fans to maintain the temperature you set. This new method provides more accurate temperature control, limits fan noise and guarantees negative pressure inside the room. Simply plug in your fans set the temperature and the Pro Twin Controller will take care of the rest. The SMS MK2 twin controller slave will daisy chain to your Mk2 controller Pro enabling multiple in and out fans from the same control unit.