Thomson Marconi Sonar (TMS) was formed as Ferranti Thomson Sonar Systems (FTSS) in 1990 by the merger of the sonar systems businesses of Thomson-CSF and Ferranti. The head office of FTSS was at Cheadle Heath, Stockport, with subsidiary sites in Church Crookham, Hampshire, Weymouth, Dorset, Bridlington, Yorkshire and Rochester (this site was an ex GEC site).
GEC acquired Ferranti's share of the business in 1995 to form Thomson Marconi Sonar.
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, renamed Thales, to purchase its stake in 2001. The company was renamed Thales Underwater Systems.
- Submarine sonar and surface ship sonar
- Minehunter sonar
- Airborne acoustic processors and dipping sonars (helicopter applications)
- Sonar support systems and trainers
- Communication systems