UNIT NAME OF LIGHT MARK KIND OF LIGHT 1 Statement truth value _V_₁ to _V_₁₂ Small, red 13 Main truth value Large, yellow The answer to a problem is shown by a pattern of the lights of Units 1 and 13. The pattern of lights is equivalent to a row of the truth table. Each little red light (Unit 1) glows when its statement is assumed to be true, and it is dark when its statement is assumed to be false. The yellow light (Unit 13) glows when the whole compound statement is calculated to be logically true, and it is dark when the whole compound statement is calculated to be logically false. The machine turns its “attention” automatically to each line of the truth table one after the other, and pulses are fed in according to the pattern of assumed true statements. We can set the machine to stop on true cases or on false cases or on every case, so as to give us time to copy down whichever kind of results we are interested in. When we have noted the case, we can press a button and the machine will then go ahead searching for more cases. A COMPLETE AND CONCRETE EXAMPLE The reader may still be wondering when he will see a complete and concrete example of the application of the logical-truth calculator. So far we have given only pieces of examples in order to illustrate some explanation. Therefore, let us consider now the following problem: PROBLEM. The A. A. Adams Co., Inc., has about 1000 employees. About 600 of them are insured under a contract for group insurance with the I. I. Insurance Co. Mr. Adams decides that more of his employees ought to be insured. As a part of his study of the change, he asks his manager in charge of the group insurance plan, “What are the possible statuses of my employees who are not insured?” The manager replies, “I can tell you the names of the men who are not insured, and all the data you may want to know about them.” Mr. Adams says, “No, John, that won’t be enough, for I need to know whether there are any groups or classes that for some basic reason I should exclude from the change I am considering.” So the manager goes to work with the following 5 statuses and the following 5 rules, and he produces the following answer. Our question is, “Is he right, or has he made a mistake?” _Statuses._ A status for any employee is a report about that employee, answering all the following 5 questions with “yes” or “no.” 1. Is the employee eligible for insurance? 2. Has the employee applied for insurance? 3. Has the employee’s application for insurance been approved? 4. Does the employee require a medical examination for insurance? 5. Is the employee insured? _Rules._ The rules applying to employees are: