{"id":5827,"date":"2022-02-15T15:34:59","date_gmt":"2022-02-15T15:34:59","guid":{"rendered":"https:\/\/loadzx.com\/sinclairworld\/?page_id=5827"},"modified":"2025-09-25T10:41:52","modified_gmt":"2025-09-25T10:41:52","slug":"cambridge","status":"publish","type":"page","link":"https:\/\/loadzx.com\/sinclairworld\/cambridge\/","title":{"rendered":"Cambridge (1973-77)"},"content":{"rendered":"\t\t
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1973<\/div>
Sinclair Radionics<\/div><\/div>
<\/i><\/div>
<\/div>
Sinclair Cambridge - Type 1<\/div>
\"\"<\/div>

The first in the Cambridge calculator range, this model can be recognised by its \u201cC\u201d clear key and separate \u201cK\u201d constant key. It featured a red eight-digit LED display and weighed under 100 grams\u2014small even by today\u2019s standards and among the lightest pocket calculators then available. Buyers could choose between a more expensive ready-made unit or a kit for home assembly. It was initially priced at around a week\u2019s average wages, though prices fell sharply within two years. The Cambridge line later grew to include many variations.<\/p><\/div><\/div><\/div>

1973<\/div>
Sinclair Radionics<\/div><\/div>
<\/i><\/div>
<\/div>
Sinclair Cambridge - Type 2<\/div>
\"\"<\/div>

This compact brown calculator was part of Sinclair\u2019s second major calculator series, designed to be light, low-cost, and easy to assemble. It offered basic arithmetic functions and replaced the \u201cK\u201d constant key\u2014used to repeat a number in successive calculations\u2014with automatic constants on all operations. A clear entry \u201cCE\u201d key was also added, allowing <\/span>users correct the most recent digit without starting over. <\/span>Introduced just a year after the Executive, the Cambridge range was sold fully assembled or as a DIY electronics kit for home assembly.<\/span><\/span>\u00a0<\/span><\/p><\/div><\/div><\/div>

C. 1973-75<\/div>
Sinclair Radionics<\/div><\/div>
<\/i><\/div>
<\/div>
Sinclair Cambridge - Type 3<\/div>
\"\"<\/div>

This model in the Cambridge range combined a constant key \u201cK\u201d with a dual-function clear key \u201cCE\u201d\u2014one press erased the last entry, two presses cleared the entire calculation. It featured a<\/span>n easy to read<\/span> red LED display, ran on four AAA batteries, and was powered by a General Instruments chip. <\/span><\/span>Like other Sinclair calculators, it was sold pre-assembled or as a DIY kit, often advertised for mail order.<\/span> <\/span>It remained compact and lightweight, weighing under 100 grams.<\/span><\/span>\u00a0<\/span><\/p><\/div><\/div><\/div>

C. 1973-74<\/div>
Sinclair Radionics<\/div><\/div>
<\/i><\/div>
<\/div>
Sinclair Cambridge Memory - Type 1<\/div>
\"\"<\/div>

This early memory model introduced a basic memory function to Sinclair\u2019s four-function Cambridge calculator. This allowed users to store a number during a calculation and retrieve it later \u2014 useful for working with running totals or repeated values. Its black casing, powered by four AAA batteries, housed a General Instruments processor and an eight-digit red LED display. Available fully built or as a kit, the Type<\/span><\/span>\u202f<\/span><\/span>1 <\/span>remained compact and convenient for home or classroom use.<\/span><\/span>\u00a0<\/span><\/p><\/div><\/div><\/div>

C. 1975<\/div>
Sinclair Radionics<\/div><\/div>
<\/i><\/div>
<\/div>
Sinclair Cambridge - Type 4<\/div>
\"\"<\/div>

This later variation of the Cambridge calculator introduced a <\/span>percentage key\u2014simplifying calculations for sales, tax, or interest\u2014<\/span>alongside separate clear \u201cC\u201d and clear-entry keys \u201cCE\u201d\u2014offering more flexibility for everyday calculations. It retained the eight-digit LED display of earlier models but ran on just two AAA batteries, making it lighter than previous versions. By the time this model was released, the price of Cambridge calculators had dropped to a fifth of their original cost\u2014part of Sinclair\u2019s push to make electronic calculators affordable for a mass market.<\/span><\/span>\u00a0<\/span><\/p><\/div><\/div><\/div>

C. 1975<\/div>
Sinclair Radionics<\/div><\/div>
<\/i><\/div>
<\/div>
Sinclair Cambridge % - Renault Ed.<\/div>
\"\"<\/div>

This version of the Cambridge calculator <\/span>was made in Spain and <\/span>appears technically identical to the Type<\/span><\/span>\u202f<\/span><\/span>4 model, with a percentage key alongside separate clear \u201cC\u201d and clear-entry \u201cCE\u201d keys, but features a different label\u2014possibly to emphasise its % function. It was likely produced as part of a promotional campaign branded for the car manufacturer Renault. In the 1970s, calculators were increasingly used as corporate gifts, reflecting a broader trend in branded technology and <\/span>lifestyle <\/span>merchandising. This object illustrates how consumer electronics also became tools of marketing and brand identity.<\/span><\/span>\u00a0<\/span><\/p><\/div><\/div><\/div>

C. 1975<\/div>
Sinclair Radionics<\/div><\/div>
<\/i><\/div>
<\/div>
Sinclair Cambridge Memory % - Type 2<\/div>
\"\"<\/div>

This silver-toned model expanded on the original Cambridge Memory by adding a percentage key. It used the same processor as Type<\/span><\/span>\u202f<\/span><\/span>1 but required only two AAA batteries, making it lighter and more compact. Its combination of memory and percentage functions aimed to support more flexible everyday use, while preserving the LED display and pocketable form. However, users sometimes found it hard to switch off\u2014a common fault caused by oxidation in the tin-coated switch contacts, used instead of more reliable gold-plated parts.<\/span><\/span>\u00a0<\/span><\/p><\/div><\/div><\/div>

C. 1975-76<\/div>
Sinclair Radionics<\/div><\/div>
<\/i><\/div>
<\/div>
Sinclair Cambridge Memory % - Type 2<\/div>
\"\"<\/div>

This particular example combines features of two Cambridge models. Although functionally a Type 2 model, with a percentage key, memory functions, and two-AAA power supply, this calculator shares the black casing and red LED display of the earlier Type 1. Its blue and grey keys provide the familiar Sinclair layout for basic arithmetic, percentage, and stored values. A thin white line appears above the Sinclair logo\u2014an unusual feature not seen on other known examples. The name \u201cGordon Smith\u201d was once inscribed on the exterior and remains etched inside the case\u2019s battery cover. Such personalisation hints at the calculator\u2019s individual history alongside its mass-produced origins.<\/p><\/div><\/div><\/div>

C. 1975-77<\/div>
Sinclair Radionics<\/div><\/div>
<\/i><\/div>
<\/div>
Sinclair Cambridge Programmable<\/div>
\"\"<\/div>

This late addition to the Cambridge range allowed users to write and store short <\/span>programmes<\/span> using a 36-step memory. It supported memory storage, brackets, and conditional jumps\u2014advanced features for a calculator of its size and price. The model was supplied with a booklet of examples, and users could also buy a library of 294 <\/span>additional<\/span> programmes<\/span>, published in four booklets. Powered by a single PP3 battery, it featured an enlarged rear casing that could make the calculator wobble on flat surfaces\u2014a design also seen in a few other Cambridge models.<\/span><\/span>\u00a0<\/span><\/p><\/div><\/div><\/div>

C. 1975-1977<\/div>
Tandy Radio Shack<\/div><\/div>
<\/i><\/div>
<\/div>
Radio Shack EC-4001 Programmable<\/div>
\"\"<\/div>

This calculator is functionally identical to the Sinclair Cambridge Programmable but feature the logo of American electronics chain Radio Shack. It included 36 programmable steps, memory, brackets, and branching instructions\u2014features rarely found at this price point. While visually nearly indistinguishable, including its white plastic case, from Sinclair\u2019s model, its branding reflects how programmable calculators began reaching broader international markets through major retail distributors.<\/span><\/span>\u00a0<\/span><\/p><\/div><\/div><\/div>

C. 1976<\/div>
Sinclair Radionics<\/div><\/div>
<\/i><\/div>
<\/div>
Sinclair Cambridge Memory % - Type 3<\/div>
\"\"<\/div>

Housed in bright red plastic, this was the most distinctive of the Cambridge Memory models. Type<\/span><\/span>\u202f<\/span><\/span>3 introduced a revised keyboard layout with memory \u201cM\u201d and dual-function clear \u201cC\/CE\u201d keys. <\/span><\/span>Unlike earlier Cambridge models that used AAA batteries, this version was powered by a <\/span>9-volt<\/span> PP3 battery, which <\/span>required<\/span> a bulging rear casing\u2014earning it the nickname \u201cpregnant\u201d model.<\/span> <\/span>It featured a Mostek integrated circuit and red LED display. By the mid-1970s, features like memory and percentage functions were becoming standard, even in budget pocket calculators.<\/span><\/span>\u00a0<\/span><\/p><\/div><\/div><\/div>

1976<\/div>
Sinclair Radionics<\/div><\/div>
<\/i><\/div>
<\/div>
Sinclair Cambridge Scientific<\/div>
\"\"<\/div>

This model marked a shift in the Cambridge range, offering functions for scientific and engineering use\u2014not just basic arithmetic. It could handle angles in degrees or radians, display results in scientific or standard notation, and store values in memory. The <\/span>bright<\/span> LED screen displayed up to eight digits, powered by two AA batteries. At the time, its relatively low cost made it an attractive option for students and professionals looking for an affordable, pocket-sized scientific calculator<\/span><\/p><\/div><\/div><\/div>

1977<\/div>
Sinclair Radionics<\/div><\/div>
<\/i><\/div>
<\/div>
Sinclair Cambridge Universal<\/div>
\"\"<\/div>

This expanded model in the Cambridge range added square root, square, percentage, and memory functions to the standard four. Like some other Sinclair calculators, it used a <\/span>9-volt<\/span> (PP3)<\/span> battery<\/span> housed in a raised rear compartment. This protruding cover made the device less stable on flat surfaces, often causing it to wobble when pressed. With a red LED display and white plastic body, <\/span>the Universal<\/span> reflected Sinclair\u2019s effort to offer more features in the original range at a time of falling prices and growing competition.<\/span><\/span>\u00a0<\/span><\/p><\/div><\/div><\/div>

1977<\/div>
Sinclair Radionics<\/div><\/div>
<\/i><\/div>
<\/div>
Sinclair Cambridge Universal - Plessey Ed.<\/div>
\"\"<\/div>

This version of the Cambridge Universal calculator appears identical in function and design, but features Plessey branding\u2014a likely promotional collaboration. Plessey, a major British electronics company, had early ties to Clive Sinclair, who used their discarded transistors in his early hi-fi kits. By the late 1970s, promotional calculators were widely used as branded corporate gifts. This object highlights how Sinclair\u2019s products served both consumer and marketing roles in a rapidly evolving electronics landscape.<\/span><\/span>\u00a0<\/span><\/p><\/div><\/div><\/div><\/div>\n

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