Fig. 53 illustrates one style of electric thermostat that is very generally used for temperature regulation in the average dwelling. It consists of three distinct parts--the controller, the electric battery and the motor. In the drawing the motor is shown connected with a steam valve, such as may be used for furnishing steam for a series of radiators. It may with equal facility be attached to the dampers of a furnace or other heating apparatus. The controller occupies a place on the wall of the room to be heated and makes electric connections between the battery and the motor. Whenever the temperature varies from the required degree, a change of electric contact in the controller starts the motor, and the radiator valve or the furnace drafts are opened or closed as occasion requires. The controller appears in Fig. 54 as commonly seen in use. The upper part carries a thermometer and the pointer _A_ indicates the temperature to be maintained in the room. The middle division indicates 70°F. Each division to the right of the middle point raises the temperature 5°. Each division to the left lowers the temperature a like amount. In addition to the ordinary type this controller is furnished with a time attachment by means of which the controller may permit the temperature of the room to fall to any desired degree at night and raise it again in the morning at the time for which it is set. This is accomplished by a little alarm clock shown at the bottom of the controller in Fig. 54. The indicator _B_ is arranged to correspond with the indicator _A_; the middle point representing 70°F. To set the time attachment, the alarm is wound and set as in any alarm clock, 1/2 hour earlier than the desired time for rising. The indicator _B_ is set for the day temperature and _A_ is set for the temperature desired during the night. At the appointed time the alarm moves the indicator _A_ to the desired point for the day and the controller raises the temperature accordingly.