CONSTRUCTION AND COMPLETION OF THE
KALIN-BURKHART LOGICAL-TRUTH CALCULATOR
With the designs in mind, Kalin and Burkhart bought some war surplus materials, including relays, switches, wires, lights, and a metal box about 30 inches long by 16 inches tall, and 13 inches deep. From March to June, 1947, they constructed a machine in their spare time, assembling and mounting the parts inside the box. The total cost of materials was about $150. In June the machine was demonstrated in Cambridge, Mass., before several logicians and engineers, and in August it was moved for some months to the office of a life insurance company. There some study was made of the possible application of the machine in drafting contracts and rules.
GENERAL ORGANIZATION
OF THE MACHINE
The logical-truth calculator built by Kalin and Burkhart is not giant in size, although giant in capacity. Like other mechanical brains, the machine is made up of many pieces of a rather small number of different kinds of parts. The machine contains about 45 dial switches, 23 snap switches (or two-position switches), 85 relays, 6 push buttons, less than a mile of wire, etc. The lid of the metal box is the front, vertical panel of the machine.
UNITS OF THE MACHINE
The machine contains 16 units. These units are listed in [Table 11], in approximately the order in which they appear on the front panel of the machine—row by row from top to bottom, and from left to right in each row.
Table 11
| UNITS, THEIR NAMES, AND SIGNIFICANCE | ||||||
|---|---|---|---|---|---|---|
| Unit | Row | Part | No. | Mark | Name | Significance |
| 1 | 1 | Small red lights | 12 | — | Statement truth- value lights | Output: glows if statement is assumed true in the case |
| 2 | 1 | 2-position snap switches | 12 | ~ | Statement denial switches | Input: if up, statement is denied |
| 3 | 2 | 14-position dial switches | 12 | V | Statement switches | Input of statements |
| 4 | 3 | 4-position dial switches | 11 | k | Connective switches | Input of connectives: ∧ (and), ∨ (or), ▲ (if-then), ▼ (if and only if) |
| 5 | 4 | 11-position dial switches | 11 | A | Antecedent switches | Input of antecedents |
| 6 | 5 | 11-position dial switches | 11 | C | Consequent switches | Input of consequents |
| 7 | 6 | 2-position snap switches | 11 | S | Stop switches | Input: if up, associates connective to main truth-value light |
| 8 | 6 | 2-position snap switches | 11 | ~ | Connective denial switches | Input: if up, statement produced by connective is denied |
| 9 | 7 | Red light and large button | 1 | Start | Automatic start | Input: causes the calc. to start down a truth table automatically |
| 10 | 7 | Red light and 2 buttons | 1 | Start Stop | Power switch | Input: turns the power on or off |
| 11 | 7 | 2-position snap switch and red button | 1 | Stop | “Stop-on-true-or- false” switch | Input: causes the calc. to stop either on true cases or on false cases |
| 12 | 7 | Yellow light | 1 | — | Main truth-value light | Output: glows if the statement produced by the main connective is true for the case |
| 13 | 7 | Large button | 1 | Man. Pulse | Manual pulse button | Input: causes the calc. to go to the next line of a truth table |
| 14 | 7 | 11-position dial switch | 1 | kⱼ | Connective check switch and light | Output: glows when any specified connective is true |
| 15 | 7 | 13-position dial switch | 1 | TT Row Stop | “Truth-table-row- stop” switch | Input: causes the calc. to stop on the last row of the truth table |
| 16 | Be- tween 6 & 7 | Continuous dial knob and button | 1 | — | Timing control knob | Input: controls the speed at which the calculator scans rows of the truth table |
Some of the words appearing in this table need to be defined. Connective here means “and,” “or,” “if ··· then,” “if and only if.” Only these four connectives appear on the machine; others when needed can be constructed from these. The symbols used for these connectives in mathematical logic are ∧, ∨, ▲, ▼. These signs serve as labels for the connective switch points. In this machine, when there is a connective between two statements, the statement that comes before is called the antecedent and the statement that comes after is called the consequent.