|Calculators and Adding Machines|
|Felt & Tarrant Model J Comptometer|
Comptometer-style mechanical calculators were once among the most common and popular forms of adding machine available. Though Felt & Tarrant originally invented and marketed the actual Comptometer brand calculating device, the word 'comptometer' has since become the vernacular. Comptometers are characterized by their massive array of keys. Unlike a modern calculator which only has a single set of numeric keys and forces the user to enter numbers one digit at a time, comptometers have a column of numeric keys for each digit. This allows a skilled operator to add numbers on the machine at a very fast pace, far faster than on a conventional calculator, by striking every column of keys at once. Comptometers are designed primarily for repetitive addition. Though capable of other mathematical operations, execution is not so straightforward. In fact, most of the entities that manufactured Comptometer-style calculators ran academies which companies could send their employees to, in order to learn how to operate these machines.
|Lightning Portable Adding Machine|
The Lightning Portable Adding Machine is a device commonly referred to as an 'addometer', a popular type of calculator in the 1950s and 1960s due to their low cost and ease of use. Unlike complex comptometers and expensive 10-key calculators, addometer-style machines could be used by practically anyone, with little to no training. The controls of the machine consist of seven perforated wheels which resemble small rotary phone dials. Four of the dials are copper-colored; these dials are the cents and thousands indicators when working with currency. The perforations in the dials are marked with numbers.
The Addometer is a small, handheld, stylus operated adding machine that was produced in large quantities during the first half of the 20th century. The machine consists of a set of 8 digit wheels encased in a long rectangular metal enclosure with carry levers located above each wheel. Using the machine for addition is very simple; the stylus is inserted in the hole for the desired number on each dial and turned clockwise to add it to the total, which appears in the small round windows at the bottom of each dial. The machine can also be used for subtraction, in this mode the dials are turned counterclockwise and the smaller numbers are used for input. A sliding lever on the side of the device can be pulled out to reset the machine to zero. The Addometer was manufactured for nearly 40 years starting in 1927, and as such is quite common in the collectors market.
The Craig 4505 is a small, horizontal format four-function calculator that was first released in 1974. Numerous calculators were made in this horizontal layout in the 1970s, in which the keypad is located to the right instead of below the display. This calculator makes use of a 9 digit, tubular single envelope VFD, similar to the Futaba 9CT06 or Soviet-made IV-21 tube. The Craig 4505 makes use of a Rockwell 15330 calculator-on-a-chip IC to handle most of its functions, this chip is located in a square cutout in the PCB directly below the display. In 1974, the list price for this calculator was $110 US dollars.
|Todd Protectograph Co. 'Star' Adding Machine|
The Todd Protectograph 'Star' adding machine is quite small when compared to a comptometer from the same era, such as the Felt & Tarrant Model J. The front of the machine is bristling with ribbed sliders by which numbers are entered into the device. Each rib is labeled with a number mounted to an adjacent plate. To enter a number into the device, the user places their finger onto the appropriate rib and then pulls the slider down until their finger had pushed down the small button at the base of each slider. This is quite analogous to the operation of the digits dial on a rotary telephone.
|Texas Instruments Business Analyst|
The Business Analyst is a common finance-oriented derivative of the Texas Instruments TI-30 and was released in 1976. The calculator has a nine digit LED display, one digit of which is reserved for the displaying the sign. Each digit has a convex magnifier lens attached to increase the readability of the tiny die-based LED strip display. The calculator uses rechargeable batteries which can be recharged while installed inside the calculator, though any original batteries have likely erupted into a blob of green corrosion long ago. This calculator uses a TMC0982 chip, the same chip as used in the extremely popular TI-30 calculator. This particular example was manufactured in the 18th week of 1977, and would have originally sold for $49.95.
|Victor 6834 Adding Machine|
The Victor 6834 uses a comptometer-style input system, with a row of sequential input keys for each digit. Although this machine is capable of displaying up to nine digits, only eight of then have input keys, as is normal for comptometers. The unit has no display; each number entered into the machine is printed on a standard roll of adding machine paper that is loaded into the back of the device.
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