Sinclair Cambridge
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The Sinclair Cambridge was a pocket-sized
calculator An electronic calculator is typically a portable electronic device used to perform calculations, ranging from basic arithmetic to complex mathematics. The first solid-state electronic calculator was created in the early 1960s. Pocket-sized ...
introduced in August 1973 by
Sinclair Radionics Sinclair Radionics Ltd was a company founded by Sir Clive Sinclair in Cambridge, England which developed hi-fi products, radios, calculators and scientific instruments. History After raising funds to start the business by writing articles ...
. It was available both as kit form kit to be assembled by the purchaser, or assembled prior to purchase. The range ultimately comprised seven models, the original "four-function" Cambridge, which carried out the four basic mathematical functions of addition, subtraction, multiplication, and division, being followed by the Cambridge Scientific, Cambridge Memory, two versions of Cambridge Memory %, Cambridge Scientific Programmable and Cambridge Universal.


History

The Cambridge had been preceded by the
Sinclair Executive The Sinclair Executive was the world's first "slimline" pocket calculator, and the first to be produced by Clive Sinclair's company Sinclair Radionics. Introduced in 1972, there were at least two different versions of the Sinclair Executive, wi ...
, Sinclair's first pocket calculator, in September 1972. At the time the Executive was smaller and noticeably thinner than any of its competitors, at , fitting easily into a shirt pocket. A major factor in the Cambridge's success was its low price; the Cambridge was launched in August 1973, selling for ( +
VAT A value-added tax (VAT), known in some countries as a goods and services tax (GST), is a type of tax that is assessed incrementally. It is levied on the price of a product or service at each stage of production, distribution, or sale to the en ...
) fully assembled or ( + VAT) as a kit. An extensive manual explained how to calculate functions such as
trigonometry Trigonometry () is a branch of mathematics that studies relationships between side lengths and angles of triangles. The field emerged in the Hellenistic world during the 3rd century BC from applications of geometry to astronomical studies. T ...
, n-th root extraction and compound interest on the device.


Design

The Cambridge was extremely small for a calculator of the time: it weighed less than and its size was . Power was supplied by four
AAA batteries The AAA battery (or triple-A battery) is a standard size of dry cell battery. One or more AAA batteries are commonly used in low-drain portable electronic devices. A zinc–carbon battery in this size is designated by IEC as R03, by ANSI C18.1 ...
. The use of cheap components was an important contributor to the unit's cost. A common failure mode was with the switch contacts, making it impossible to switch the calculator off. Due to the use of switch contacts made of nickel coated with tin, rather than gold, an
oxide An oxide () is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– (molecular) ion. with oxygen in the oxidation state of −2. Most of the E ...
layer would be smeared across the insulating barrier after repeatedly using the switch.


Display

Numbers were displayed on the 8-digit
LED A light-emitting diode (LED) is a semiconductor Electronics, device that Light#Light sources, emits light when Electric current, current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy i ...
display (made by National Semiconductor) in scientific format with a 5-digit mantissa and a 2-digit exponent. The Cambridge used
light-emitting diode A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (cor ...
s for its display. On later scientific variants the power draw for the display required a larger
PP3 battery The nine-volt battery, or 9-volt battery, is an electric battery that supplies a nominal voltage of 9 volts. Actual voltage measures 7.2 to 9.6 volts, depending on battery chemistry. Batteries of various sizes and capacities are manufactured; ...
, creating a bulge in the lower rear casing of the appliance.


Variants

A later model, the Sinclair Cambridge Scientific, was developed, and launched in March 1974 at a price of £49.95 (£5 cheaper than its nearest rival from Hewlett-Packard). As the name suggests, it was a development of the Cambridge, using the same case, with the addition of some common scientific functions (sin, cos, tan, etc.). The other calculators in the range were the Cambridge Memory, Cambridge Memory % (which came in two different versions), Cambridge Programmable (marketed in the United States as the Radio Shack EC-4001), Cambridge Scientific, Cambridge Scientific Programmable and Cambridge Universal. The Cambridge Programmable (sold in the U.S as the Radio Shack EC-4001) was released in 1975. It lacked accuracy in many of its scientific functions, some yielding only four
significant digit Significant figures (also known as the significant digits, ''precision'' or ''resolution'') of a number in positional notation are digits in the number that are reliable and necessary to indicate the quantity of something. If a number expres ...
s. It featured a single
memory register A processor register is a quickly accessible location available to a computer's processor. Registers usually consist of a small amount of fast storage, although some registers have specific hardware functions, and may be read-only or write-only. ...
and a limit of 36 program steps, along with a
conditional jump A branch is an instruction in a computer program that can cause a computer to begin executing a different instruction sequence and thus deviate from its default behavior of executing instructions in order. ''Branch'' (or ''branching'', ''branc ...
instruction. The Programmable came with a program library consisting of 4 books, covering general functions, finance & statistics, mathematics, physics & engineering and electronics. The Cambridge Programmable was superseded by the Sinclair Enterprise, which allowed 80 program steps.


References


Citations


Sources

* {{Sinclair calculators Sinclair calculators Computer-related introductions in 1973