The recent Fukushima accident has posed several challenges to nuclear community with respect to safety of the nuclear power plants (NPPs) during simultaneous occurrence of seismic, Tsunami, multiple failures of safety systems and also maintaining the long term sub criticality during these events. Safety Instrumented Systems (SISs) are used in many application areas to reduce the likelihood of such severe accidents and/or to mitigate the consequences. An indigenously developed seismic switch is employed to safely shut down the reactor upon the occurrence of a seismic event. The reliability of seismic switch is of vital importance to ensure safe operation of a NPP. This paper presents the results of reliability study performed on digital and analog seismic switches to assess their performance.