Last week, Sir Clive Sinclair, British inventor of the ZX Spectrum personal computer, passed away at the age of 81. 

With a career that spanned more than four decades, Sinclair had many notable achievements in the world of business, electrical engineering, and computing. Naturally, he also experienced a few setbacks along the way.

In a 2020 vignette of his life, the BCS Chartered Institute for IT remarks, "Probably only electronics hobbyists in the 1960s and students of electronics in the 1970s remember Sinclair for his miniature radio kits and audio amplifiers, and that with varying degrees of pleasure."

Sir Clive Sinclair. Image used courtesy of BCS Chartered Institute for IT

Although Sinclair was not classically trained as an engineer, he was a maker at heart and struck a chord with many hobbyists in the UK and beyond. As a consummate entrepreneur, he embodied the spirit of innovation and possessed a visionary view of the future. Occasionally, that vision led him to a product concept that was not ready for market capitalization in the UK, as was the case with the Sinclair C5 electric car in 1985. 

Still, many of his developments saw commercial success, and the early years of his career were both financially and technologically fruitful. 

Sinclair's Early Years (1962–1979)

Sir Clive Sinclair graduated secondary school at 17 and went straight to the workforce. After a stint in technology journalism, he went on to form the first of his companies—Sinclair Radionics, which focused on mail-order amplifiers and radio kits.

Commenting on the ease of this business model, Sinclair explained, "What you needed was a soldering iron, it came with a printed circuit board and it wasn’t too difficult." Sinclair assembled many of these micro-amplifiers and inexpensive pocket radios from his kitchen table using cheap transistors from Plessey, a British electronics company. 

Buoyed by the financial success of his initial venture, Sinclair eventually branched out into the world of pocket calculators and eventually topped the market in the UK for calculator sales. 

Sir Clive Sinclair and the ZX Spectrum home computer. Image used courtesy of Peter Jordan/Alamy and The Guardian

Sinclair’s primary innovation was the miniaturization of pocket calculators. Counterparts of the day contained a battery that was too big and bulky to slip into a pocket. The first Sinclair pocket calculator was powered by a microchip that was half the price and size of comparable calculators of the time.

Sinclair addressed the power issue with a form of PWM, where the device would only be powered 10 percent of the time. As a result, the calculator could be powered by a much smaller coin cell battery. This advantage was key to his early successes. 

A Sinclair pocket calculator (shown in 2006). Image used courtesy of Calyx/Rex and The Guardian

In 1972, Sinclair created the slimline calculator, "Sinclair Executive," which was a portable pocket calculator capable of only basic math functions but was nonetheless a symbol of status at the time. During this stage of Sinclair's career, he also teamed up with his brother (an industrial designer) to build hi-fi kits, including amplifiers and turntables. 

The third decade of his career solidified his achievements in the annals of computing and even inspired a museum based largely on his ZX Spectrum home computers. 

The Halcyon Days of Home Computers (1979–1986)

In 1979, Sinclair founded Sinclair Research and became one of the forerunners of the home computer revolution. Before the 80s, many people still thought of computers as giant room-sized machines. This notion began to change with Sinclair's first cheap personal computer, the ZX80, which measured 9 inches wide and 7 inches deep. The ZX80 specifications show that the CPU operated at 3.25 MHz with 4k ROM and 1K RAM. 

To access a screen and memory storage, this device needed to be plugged into both a television set and a cassette. 

The ZX80 home computer (1979). Image used courtesy of LOAD ZX Spectrum Museum

Selling this computer for less than £100 brought in sales revenue, and in 1982, the ZX81 launched. The ZX81 was said to be unparalleled at the time; it contained only four integrated chips when the competition was using forty-six. Sinclair Research sold a quarter of a million of these machines by 1981 with no commercial rivals in the first year of sales.

In 1983, Sinclair was knighted for services to industry and the University of Bath granted him an Honorary Doctor of Science degree. In the following years, Sinclair became interested in electric bicycles, developing an e-bike dubbed "Zike," a bike battery engine, and a commuter A-bike that could be folded up. 

Although best known for his early work in computing, Sir Clive Sinclair’s legacy is reflected in many of the successful designs we see today.

Sir Clive Sinclair’s Legacy

In 1985, Sinclair invented the C5 electric vehicle prototype—an unsuccessful venture. The lightweight vehicle sported plastic sides and three wheels and topped at 15 mph speeds. It also required charging after only 20 miles. Beyond the C5, Sinclair innovated the aforementioned Zike bicycle, which he transformed into an electric unit with the ZETA kit.

Sinclair demonstrating the C5 electric vehicle in 1985. Image used courtesy of The Guardian 

Sinclair’s Button Radio in 1997 resurged his passion for miniaturization and radio technology. The Button Radio was a complete FM receiver with full tunable bands from 88 MHz to 108 MHz, which fit around the ears—an early iteration of the in-ear headphones today.

Finally, many see the Raspberry Pi and other homebrewed computers like the MISTer-modified DE10 Nano as a natural evolution of the first home computers. Even Raspberry Pi founder Eben Upton reports playing with his cousin's ZX Spectrum growing up. These computing platforms are a fitting tribute to those earliest days of home computers and the makers, like Sir Clive Sinclair, who made them.