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ClearSy launches its SIL4-certified range of safety critical relays

05 December 2017
by ubi -- last modified 05 December 2017

The six safety critical relays developed by ClearSy France are the first self-controlled safety critical relays to guarantee opening of their NO contacts at SIL4 level. SIL4-certified since 2016, they are in compliance with the EN 50129 and EN 50155 standards.



ClearSyApplications of these relays include:

  • Tram level-crossing protection systems (Lyon, France)
  • On-board tram control system (Nice, France)
  • Tram SIL 4 signalling system (Luxembourg, France)

The availability of these relays with NO contacts guarantee on opening and independently SIL 4 certified is a first on the railway market.

Suited to the railway market's needs

RS4-range relays are available with different control voltages, from 24 to 110 Volts. Models have 2 to 4 make contacts (NO) and 2 to 6 (NC) break contacts.

Available in two formats, a DIN rail box or a 3U card, these relays provide galvanic isolation between control and contacts.

'Our relays are designed for even the harshest environments (-40° C to +70°C) with high vibrations and/or shocks and salt spray. They are fit for all conditions', explains Patrick Péronne, project manager at ClearSy.

The RS4 range constitutes significant technological progress for on-board and/or trackside critical control applications.

'A single RS4 safety critical relay provides galvanic isolation in a very compact format and reduces the number of contacts in safety applications without the need for auxiliary contacts for copying. It also provides contacts able to make even with very low current, an important aspect for all applications requiring an interface with PLC', points out Patrick Péronne.

Technical specifications of the RS4 range

Technical specifications of the RS4 range


  • Use of two internal relays. Each NO contact in the RS4 relay corresponds to two internal relay contacts placed in series. If a NO contact in one of the internal relays jams, the NO contact of the RS4 relay remains open.
  • Restriction of the RS4 control if a contact in one of the two internal relays jams. Accordingly, it is impossible to have the two internal relays of the RS4 relay with contacts jammed at the same time.
  • The restriction principle of the SIL4 control is validated by an official certifier (as per everything else concerned with the relay)
  • Internal relays with guided contact that meet standard EN 50205 (to guarantee checking of contacts and non-overlap between make and break contacts)
  • Hermetically-sealed relays to guarantee that contacts do not oxidise
  • Diversifying of components to supress common modes.
  • Impossibility of a short circuit (insulation distance, hermetically-sealed internal relay boxes…)


  • PCB and assembly rule IPC 610 class 3
  • Full safety and functional test on each relay produced
  • IRIS-certified manufacturing site
  • ClearSy and its ISO 9001-qualified service provider

The RS4 range

More about ClearSy
ClearSy develops and markets SIL1- to SIL4-certified safety systems. Established in 2001 and based in Aix-en-Provence (France), the independent company employs more than 100 people specialised in the production of SIL1 to SIL4 safety-critical systems and software.

From design to commissioning, the company is unique in that it can have its solutions certified. This means that it can offer a high degree of safety and has worked on major projects in São Paulo (monorail) and Stockholm and in France with lines 1, 4 and 13 of the Paris metro. For these, it developed a control system for opening and closing the landing doors and ensuring the safe departure of driverless trains. Their clients include Ansaldo, Alstom, Bombardier, Siemens, the RATP Group and Thalès.

For more information, please contact:
Thierry Servat, CEO

For more information on this press release, contact:
Business France UK (The French Trade Commission)
Catherine Ryall, Press Officer,

Business France

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Business France is a government agency supporting the international development of the French economy that was formed through the merger between Ubifrance and the Invest in France Agency on January 1, 2015. It advances and promotes business throughout France, and by French companies abroad.

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