Consider a digital thermostat in which the measured room temperature is converted to a digital number and applied to the A inputs of a comparator. The desired room temperature, entered from a keypad, is stored in a register that is connected to the B inputs. If A < B, the furnace should be activated to heat the room. The furnace should continue to heat while A = B and shut off when A > B. As the room cools off, the furnace should stay off while A = B and turn on again when A < B. What digital circuit can be used to interface a magnitude comparator to a furnace to perform the thermostat control application described here?