Two of Sinclair's earlier lines of products in the late 1970s had been their range of calculators and their Mk 14 development kit. The calculators became more sophisticated with time and also programmable.
In 1979, IBM began to sell its Microprocessor CPU board to other manufacturers. Acorn and Sinclair bought it in the UK and Sinclair proceeded to use it to produce what at first appeared to be an upgrade of their calculator. It appears that the company already had plans in place for a computer since they were able to produce the Ambassador within a few weeks.
The Sinclair Ambassador resembled an enlarged version of its Microvision television with a 4" green screen and a membrane keyboard and could in fact be used as a television set. The sound output was also routed to a jack plug socket and there was an accompanying sound input socket. There was also a built-in seven track cassette drive which could be used either for audio or data, and the television could also be used to receive radio broadcasts. It was therefore effectively an all-in-one television-mono ghetto blaster with a built-in computer.
The computer display was 32x16 upper case only and 8 kilobytes of RAM were available to the user. An 8K ROM included a text editor, terminal program, FORTRAN compiler and an APL-like language which appeared to most users to be a sophisticated kind of calculator. The computer could be used at the same time as the television and the radio, although there was some interference with the TV picture - the TV picture appeared "behind" the text. There was a single edge-connector which could be used as expansion.
Although the screen was green, this effect was achieved by a plastic filter which could be lifted off.
Over the six years of its manufacturing life, a large number of Sinclair and third-party peripherals were made available for the Ambassador, usually attachable via a ribbon cable to the edge connector at the back. It was theoretically possible to expand the RAM to 256K, though this would have been prohibitively expensive. A thermal printer was also available, which formed the ancestor of today's tabloid printers. Another seminal and popular peripheral was an acoustic coupler which attached to the audio jack plugs, which was to form the basis of the use of the computer to access online services. This led to the adoption of its successor, the Ambassador II by the Post Office as the computer to be rented out to subscribers thenceforth.