Thomson Marconi Sonar or TMS was formed in 1996 by the merger of the sonar systems businesses of French defence electronics specialist Thomson-CSF and British company GEC-Marconi after the payment of a balance by the latter.^[1] The new company was 50.1% owned by Thomson-CSF and 49.9% by GEC-Marconi.^[2] Denis Ranque was appointed as its CEO. The new company would head 3 operational entities:

• The French entity, Thomson Sintra (based in Brest and Sophia Antipolis), was brought in by Thomson-CSF. It was the European leader in defence-related sonar systems and the world's second after Lockheed Martin Loral, with annual sales of 1.5 billion francs, split between submarine sonars (35%), anti-submarine warfare systems or ASM (27%), mine warfare (15%) and airborne sonars (18%).^[3]
• The British entity was made up of GEC-Marconi's sonar division, which had annual sales of 90 million pounds (700 million francs) as well as a company already co-owned by it and Thomson-CSF called Ferranti Thomson Sonar Systems (with about 400 million francs in sales).^[4]
• A third entity in Australia, called TMS Pty, was composed of the two groups' establishments operating in the sector.^[5]

With the merger of GEC's defence business Marconi Electronic Systems and British Aerospace in 1999, the resulting BAE Systems acquired Marconi's 49.9% share in TMS. BAE, through an options agreement, forced Thomson-CSF (now called Thales) to purchase its stake in 2001. The company therefore became entirely owned by Thales and was renamed Thales Underwater Systems.

Products

• Submarine sonar and surface ship sonar
• Minehunter sonar
• Airborne acoustic processors and dipping sonars (helicopter applications)
• Sonar support systems and trainers
• Communication systems