Made in 1981 by Polytechnic Marine and sold by Decca, the ‘Decca Sat Nav DS4’ is a satellite navigation receiver that worked with the Transit satellite system to determine a user’s latitude and longitude. The Decca Sat Nav DS4 was manufactured for marine markets including fishing and commercial. It was launched in January 1981 and sold for approximately £3000 ($7200). During this time period, receivers such as this one were used by Royal Navy submarines to fix their position off-shore.

The Transit satellite system was developed by the United States Navy during the Cold War to provide accurate location information to Polaris ballistic missile submarines. Transit became operational in 1964 and the technology was later made available to civilians and the commercial market. By the 1980s, thousands of warships, freighters and private watercraft used Transit. This was partly due to changes in how consumer electronics were manufactured and advances in chip technology. In the 1990s, the Transit system was made obsolete by the Global Positioning System (GPS) and ceased service in 1996.