SSL currently employs 540 people at four main locations. The acquisition increases Alstom Transport's workforce in the United Kingdom and Ireland to 2,500.
Alstom say the business will continue to trade under the SSL brand 'for the foreseeable future.'
Mr Terence Watson, President of Alstom UK, says: "Alstom will use this fantastic opportunity to strengthen its activities in UK - which include rolling stock, infrastructure, electrification and signalling – and contribute to building a better railway. The company is looking forward to further collaborating with Network Rail, Crossrail, HS2 and the British supply chain in delivering the state-of-the-art signalling technologies that will deliver the railway's digital future."