This unit of instruction on electrical sensing devices is designed especially for use with freshman vocational agriculture students. A unit plan discusses the general aims and goals, lesson titles, student and teacher activities, and references. The unit consists of four lessons. A lesson plan for each lesson provides these components: need; references; objectives; interest approach; an outline of key questions, problems, and concerns with appropriate teaching techniques and information; application and followup; and transparency masters, exercises, handouts, and/or worksheets. Lesson topics are: electric controls and control circuits, using switches to control electrical equipment, using relay devices in the electrical circuit, using magnetic or automatic electric motor control devices, and using automatic sensing control devices. (YLB)