Suppose that the valve for admitting steam to the radiators, as that in Fig. 53, is closed and that the temperature of the house is falling. The strip _C_ of the thermostat controller is moving toward _J_. When contact is made, the current from the battery _B_ energizes the magnets _H-H_ and the bar _I_ is lifted. As the bar _I_ is raised the catch _J_ is released and permits the motor to start. The bar _I_ is held suspended by the cam _M_ until the arm _L_ has made one-half revolution, when the lug _K_ drops into the depression in the cam made to receive it and the catch _J_ engages with the brake and stops the motor. [Illustration: FIG. 53.--Thermostat complete with the regulator, battery and motor, attached to a steam supply valve.] During this movement the arm _L_ has lifted the valve arm _N_ and the valve admits steam to the radiators, at the same time the contact _M_ has been shifted from the right-hand contact to the left, and the electric circuit is ready to be made in the controller at the point _K_. When the temperature has fallen a sufficient amount the controller bar _C_ will make contact at _K_ and the motor will again make a half cycle, changing the valve back to its original position. This process will be kept up so long as the motor is wound and there is sufficient fuel in the furnace to raise the temperature. Fig. 55 shows the method of connecting the electric wires from the battery to the controller. A three-wire cable connects the battery, and makes contacts as indicated at _H_, _K_ and _J_. The wires are shown attached to the motor as in Fig. 55. A wire is taken from either pole of the battery and attached to one of the ends of the magnet coil. Passing through the magnet the wire is attached to the frame of the motor. This makes the cam _M_ a part of the electric circuit. The other two wires are attached to the brass strips on each side of the arm _L_. The strips are insulated from the frame. The electric circuit through the magnet is made alternately by contact with the strips at right and left of the arm _L_. [Illustration: FIG. 54.--Thermostatic regulator with clock attachment for control of day and night temperature.] In case the motor, through neglect, runs down, a safety switch at _D_ (Fig. 53) disconnects the battery and keeps it from being discharged. This switch is shown in detail in Fig. 56. When the weight has reached its limit, the piece _C_ on the chain comes into contact with _D_ and lifting it out of contact, breaks the circuit. When the motor is again wound, _C_ engages with _E_ and restores the contact. The switch is so arranged that when open, the valve will always be closed. [Illustration: FIG. 54_A_.--Showing the clock attachments to the thermostatic regulator.] [Illustration: FIG. 55.--Mechanism of the thermostatic regulator.]