The FD978 is a double-pole single-throw (DPST) 2NC rope operated Stop Switch with heavy duty die-cast metal alloy single conduit entry housing and reset button. This FD series limit switch feature that the lockout mechanism isolates safety contacts until manually reset. This grabwire switch comes with indicator of correct rope tension and fail-safe in the event of slack or broken wire rope. It is used for the protection of exposed machinery.
Technical Datasheet: http://www.farnell.com/datasheets/6949.pdf