Sinclair Cambridge
Encyclopedia
The Sinclair Cambridge was a small pocket-sized calculator
manufactured from summer 1973 by UK company Sinclair Radionics. It was available both as a kit to be assembled by the purchaser, and assembled. 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.
, Sinclair's first pocket calculator, in the summer of 1972. At the time the Executive was smaller and noticeably thinner than any of its competitors, at 56x138x9mm, 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 initially for . In January 1974 the Cambridge was priced at £32.95 (£29.95 + VAT
) fully assembled or £27.45 (£24.95 +VAT) as a kit, bundled with an extensive manual detailing how to calculate functions such as trigonometry, n-th root extraction and compound interest on the device. Initially power was supplied by 4xAAA batteries
.
The use of cheap components was an important contributor to the unit's cost. A common failure mode was breakage of the battery contacts,making it impossible to switch the calculator off, due to the use of switch contacts made of nickel coated with tin, rather than the gold; tin, unlike gold, produces an oxide
layer when exposed to air which spreads across the insulation over time as the switch is operated, short-circuiting the switch.
The Cambridge used light-emitting diode
s for its display. On later scientific variants the power draw for the display required a larger PP3 battery
, creating a bulge in the lower rear casing of the appliance.
display (made by National Semiconductor) in scientific format with a 5-digit mantissa and a 2-digit exponent.
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 digits. It featured a single memory register and a limit of 36 program steps, along with a conditional jump 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.
Calculator
An electronic calculator is a small, portable, usually inexpensive electronic device used to perform the basic operations of arithmetic. Modern calculators are more portable than most computers, though most PDAs are comparable in size to handheld calculators.The first solid-state electronic...
manufactured from summer 1973 by UK company Sinclair Radionics. It was available both as a kit to be assembled by the purchaser, and assembled. 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 ExecutiveSinclair Executive
The Sinclair Executive was Clive Sinclair's first venture into the pocket calculator market. The Executive was the world's first "slimline" pocket calculator. It was variously described as "a piece of personal jewelry" and "at once a conversation piece, a rich man's plaything and a functional...
, Sinclair's first pocket calculator, in the summer of 1972. At the time the Executive was smaller and noticeably thinner than any of its competitors, at 56x138x9mm, fitting easily into a shirt pocket.
Design
The Cambridge was extremely small for a calculator of the time: it weighed less than 3.5 ounces (99.2 g) and its size was 50x111x28mm.A major factor in the Cambridge's success was its low price; the Cambridge was launched in August 1973, selling initially for . In January 1974 the Cambridge was priced at £32.95 (£29.95 + VAT
Value added tax
A value added tax or value-added tax is a form of consumption tax. From the perspective of the buyer, it is a tax on the purchase price. From that of the seller, it is a tax only on the "value added" to a product, material or service, from an accounting point of view, by this stage of its...
) fully assembled or £27.45 (£24.95 +VAT) as a kit, bundled with an extensive manual detailing how to calculate functions such as trigonometry, n-th root extraction and compound interest on the device. Initially power was supplied by 4xAAA batteries
AAA battery
A triple A or AAA battery is a standard size of dry cell battery commonly used in portable electronic devices. A carbon-zinc battery in this size is designated by IEC as "R03", by ANSI C18.1 as "24", by old JIS standard as "UM 4", and by other manufacturer and national standard designations that...
.
The use of cheap components was an important contributor to the unit's cost. A common failure mode was breakage of the battery contacts,making it impossible to switch the calculator off, due to the use of switch contacts made of nickel coated with tin, rather than the gold; tin, unlike gold, produces an oxide
Oxide
An oxide is a chemical compound that contains at least one oxygen atom in its chemical formula. Metal oxides typically contain an anion of oxygen in the oxidation state of −2....
layer when exposed to air which spreads across the insulation over time as the switch is operated, short-circuiting the switch.
The Cambridge used light-emitting diode
Light-emitting diode
A light-emitting diode is a semiconductor light source. LEDs are used as indicator lamps in many devices and are increasingly used for other lighting...
s for its display. On later scientific variants the power draw for the display required a larger PP3 battery
PP3 battery
A nine-volt battery, the most common of which is designated a PP3 battery, is shaped as a rounded rectangular prism. 9-volt batteries are commonly used in pocket transistor radios, smoke detectors, carbon monoxide alarms, guitar effect units, and radio-controlled vehicle controllers...
, creating a bulge in the lower rear casing of the appliance.
Display
Numbers were displayed on the 8-digit LEDLight-emitting diode
A light-emitting diode is a semiconductor light source. LEDs are used as indicator lamps in many devices and are increasingly used for other lighting...
display (made by National Semiconductor) in scientific format with a 5-digit mantissa and a 2-digit exponent.
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 digits. It featured a single memory register and a limit of 36 program steps, along with a conditional jump 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.