Addressed to the student, this manual presents terms, abbreviations, and symbols used in discussing manual or automatic control of the flow of electric current. Diagrams accompany discussion of the following types of control devices and principles of operation: Heat sensitive controls (thermostats, thermal relays), light sensitive controls (photo-electric cell), limit switches (applications and types), fractional horsepower motor starters (starting switches), time clocks, electromagnets (solenoid, relays), and switches (toggle, push button). (TA)